Search

Background and Hypothesis Clozapine is the most effective antipsychotic for treatment-resistant schizophrenia, yet a significant proportion of individuals on clozapine continue to experience disabling symptoms, despite being treated with an adequate dose. There is a need for adjunct treatments to augment clozapine, notably for negative and cognitive symptoms. One such potential agent is the glutathione precursor N -acetylcysteine (NAC). Study Design A randomized double-blind, multi-center, placebo-controlled trial for clozapine patients with enduring psychotic symptoms (n = 84) was undertaken to investigate the efficacy of adjunctive NAC (2 g daily) for negative symptoms, cognition and quality of life (QoL). Efficacy was assessed at 8, 24, and 52 weeks. Study Results NAC did not significantly improve negative symptoms (P =.62), overall cognition (P =.71) or quality of life (Manchester quality of life: P =.11; Assessment of quality of life: P =.57) at any time point over a 1-year period of treatment. There were no differences in reported side effects between the groups (P =.26). Conclusions NAC did not significantly improve schizophrenia symptoms, cognition, or quality of life in treatment-resistant patients taking clozapine. This trial was registered with "Australian and New Zealand Clinical Trials" on the 30 May, 2016 (Registration Number: ACTRN12615001273572). [ABSTRACT FROM AUTHOR]

Objective To describe the diverse upper reference limits of serum thyroid stimulating hormone on the same platform for pregnant women in China. Methods The trimester-specific and population-specific TSH reference intervals for pregnant women were established, and then 5 reference intervals on the same platform in China were compared with the reference intervals derived from the present study and the manufacturer. Results The most striking difference in the upper reference limits of TSH among 5 reference intervals on the same platform was shown at the first trimester of pregnancy. The calculated regional prevalence rates of subclinical thyroid diseases varied using the data derived from 30,771 pregnant women who visited the largest obstetric center in our district from 2008 to 2018. Conclusion We reported differences among 7 reference intervals of TSH on the same platform and showed the changing population factors significantly affected them. [ABSTRACT FROM AUTHOR]

Limiting ultraviolet radiation exposure during early childhood can significantly reduce the risk of developing skin cancer, making early childhood a critical time for sun protection strategies. This study aimed to measure sun protection practices utilized in Australian early-childhood services over the past decade and evaluate the impact of Cancer Council Australia's SunSmart Early-Childhood Program. Results are presented from cross-sectional and repeated-measures survey data, completed by directors or other staff at randomly sampled early-childhood services in 2008, 2013 and 2018 (N  =   3243). Most sun protection practices were used by a significantly greater proportion of services in 2018 relative to earlier years, such as requiring the use of sunscreen (98.4%), and sun-protective hats (99.7%) and clothing (88.8%). However, only a small and declining proportion of services (16.3%–22.4%) required the use of specific items of sun-protective clothing. SunSmart program members reported enacting significantly more sun protection practices compared to non-members, while new members showed an increase in the use of those practices relative to services whose status did not change (d  =   0.48). The results demonstrate improvements in sun protection in Australian early-childhood settings, and highlight the benefits and limitations of the SunSmart program. [ABSTRACT FROM AUTHOR]

There is a paucity in the literature examining the African American middle-class. Most studies of African Americans and Type 2 Diabetes Mellitus (T2DM) have concentrated on lower-SES individuals, or make no distinction between African Americans of varying socio-economic positions. Middle-class African Americans are vulnerable in ways often overlooked by researchers. This study quantitatively examines specific T2DM knowledge and perceptions of risk in middleclass African Americans (N=121). The majority of respondents, 70.2%, were unable to correctly identify all the warning signs of T2DM development. Only 3.3% of respondents correctly identified all risk factors provided as 'possible causes' of T2DMdevelopment. The difference between those participants who considered themselves to be at risk for T2DM development and their level of risk, according to the American Diabetes Associations' risk assessment, was not statistically significant (P=0.397). However, there were statistically significant differences between participants' perceptions of their weight and clinical definitions of overweight, a major risk factor in T2DM development, based on BMI (P=0.000). Middle-class African Americans are not inherently protected or exempt from developing T2DM. This study demonstrates gaps in knowledge and overall incongruent levels of perceived susceptibility, suggesting a need for additional research and health education in this segment of the population. [ABSTRACT FROM AUTHOR]

Background. For health care providers in the United States, the risk for nonfatal violence in the workplace is 16 times greater than that for other workers. Inappropriate patient sexual behavior (IPSB) is directed at clinicians, staff, or other patients and may include leering, sexual remarks, deliberate touching, indecent exposure, and sexual assault. Inappropriate patient sexual behavior may adversely affect clinicians, the organization, or patients themselves. Few IPSB risk factors for physical therapists have been confirmed. The US prevalence was last assessed in the 1990s. Objective. The objectives of this study were to determine career and 12-month exposure to IPSB among US physical therapists, physical therapist assistants, physical therapist students, and physical therapist assistant students and to identify IPSB risk factors. Design. This was a retrospective and observational study. Methods. An electronic survey was developed; content validity and test-retest reliability were established. Participants were recruited through physical therapist and physical therapist assistant academic programs and sections of the American Physical Therapy Association. Inappropriate patient sexual behavior risk models were constructed individually for any, mild, moderate, and severe IPSB events reported over the past 12 months. Open-ended comments were analyzed using qualitative methods. Results. Eight hundred ninety-two physical therapist professionals and students completed the survey. The career prevalence among respondents was 84%, and the 12-month prevalence was 47%. Statistical risk modeling for any IPSB over the past 12 months indicated the following risks: having fewer years of direct patient care, routinely working with patients with cognitive impairments, being a female practitioner, and treating male patients. Qualitative analysis of 187 open-ended comments revealed patient-related characteristics, provider-related characteristics, and abusive actions. Limitations. Self-report, clinician memory, and convenience sampling are limitations of this type of survey research. Conclusions. The extremely high prevalence of IPSB among physical therapist professionals warrants practitioner and student education as well as clear workplace policy and support. [ABSTRACT FROM AUTHOR]

Objective. To conduct a replication study and meta-analysis involving the study of mtDNA variants in the radiographic progression of OA in different cohorts worldwide, including Cohort Hip and Cohort Knee (CHECK), the OA Initiative and a cohort from Spain. Methods. The influence of the haplogroups in the rate of radiographic progression at 96 months in 431 subjects from CHECK was assessed in terms of Kellgren and Lawrence (KL) grade. Progression was defined as a change from KL ≥ 1 at baseline to any higher grade during the follow-up. Extended Cox proportional hazard models were used to analyse the influence of mtDNA variants in the rate of radio-graphic knee OA progression. A subsequent meta-analysis of 1603 subjects following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted to combine the data of individual studies. A sensitivity analysis was performed to validate the stability of the results. Results. CHECK subjects carrying the haplogroup T showed the lowest rate of radiographic knee OA progression [hazard ratio (HR) 0.645 (95% CI 0.419, 0.978); P < 0.05]. When pooled, subjects within the superhaplogroup JT showed the same trend [HR 0.707 (95% CI 0.501, 0.965); P < 0.05]. BMI [HR 1.046 (95% CI 1.018, 1.073); P < 0.05] and bilateral OA [HR 2.266 (95% CI 1.733, 2.954); P < 0.05] at baseline are risk factors for radiographic knee OA progression as well. In the meta-analysis there was a reduced rate of radiographic progression in subjects with haplogroup T [HR 0.612 (95% CI 0.454, 0.824); P = 0.001] or in the superhaplogroup JT [HR 0.765 (95% CI 0.624, 0.938); P = 0.009]. Sensitivity analysis revealed that the results were robust. Conclusion. The mtDNA variants in the superhaplogroup JT associate with a reduced rate of radiographic OA progression. The mtDNA polymorphisms in the superhaplogroup JT emerge as potential complementary genetic biomarkers for disease progression. [ABSTRACT FROM AUTHOR]

The U.S. federal Every Student Succeeds Act (ESSA) was enacted with goals of closing achievement gaps and providing all students with access to equitable and high-quality instruction. One requirement of ESSA is annual statewide testing of students in grades 3-8 and once in high school. Some students, including many deaf or hard-of-hearing (D/HH) students, are eligible to use test supports, in the form of accommodations and accessibility tools, during state testing. Although technology allows accommodations and accessibility tools to be embedded within a digital assessment system, the success of this approach depends on the ability of test developers to appropriately represent content in accommodated forms. The Guidelines for Accessible Assessment Project (GAAP) sought to develop evidence- and consensus-based guidelines for representing test content in American Sign Language. In this article, we present an overview of GAAP, review of the literature, rationale, qualitative and quantitative research findings, and lessons learned. [ABSTRACT FROM AUTHOR]

Background: Certain factors originating from the perinatal and childhood periods are suspected of contributing to the recent increasing trend of childhood type 1 diabetes (T1D) incidence. This study sought to investigate the relationships between various perinatal and childhood risk factors and T1D incidence in young children (<10 years). Methods: We used a nested case-control design based on 1 478 573 live births born in 2000-05 in Taiwan. Cases were 632 incident cases of T1D between 2000 and 2008. Ten matched controls for each case were randomly selected. Information on various perinatal risk factors was also identified from claim data. Multiple conditional logistic regression was employed to estimate odds ratio (OR) and 95 confidence interval (CI) of T1D. Results: Childhood infection was significantly associated with an increased risk of T1D (OR = 1.46, 95% CI = 1.23-1.73). Increased risk of T1D was also noted in children born to younger mothers (<25 years) (OR = 1.94, 95% CI = 1.34-2.81), older fathers (>30 years) (OR = 1.56 (95% CI = 1.16-2.10) to 1.57 (95% CI = 1.19-2.05), mothers with Caesarean section (CS) (OR = 2.35, 95% CI = 1.52-3.64), and mothers with gestational diabetes mellitus (OR = 4.36, 95% CI =2.76-7.77). Fathers with T1D (OR = 7.36, 95% CI = 1.02-57.21) or type 2 diabetes (OR = 1.54, 95% CI = 1.04-2.26) were observed to substantially increase the risk of offspring T1D. Conclusions: Certain modifiable perinatal factors such as infection and CS may predispose incidence of T1D in young children. [ABSTRACT FROM AUTHOR]

Background. Soft tissue massage and exercise are commonly used to treat episodes of shoulder pain. Objective. The study objective was to compare the effects of soft tissue massage and exercise with those of exercise alone on pain, disability, and range of motion in people with nonspecific shoulder pain. Design. This was a randomized controlled trial. Setting. The study was conducted in public hospital physical therapy clinics in Sydney, New South Wales, Australia. Participants. The study participants were 80 people with an average age of 62.6 years (SD=12.2) who were referred to physical therapists for treatment of nonspecific shoulder pain. Intervention. Participants were randomly assigned to either a group that received soft tissue massage around the shoulder and exercises (n=40) or a group that received exercise only (n=40) for 4 weeks. Measurements. The primary outcome was improvement in pain, as measured on a 100-mm visual analog scale, 1 week after the cessation of treatment. Secondary outcomes were disability and active flexion, abduction, and hand-behind-back range of motion. Measurements were obtained at baseline, 1 week after the cessation of treatment, and 12 "weeks after the cessation of treatment. Results. The between-group difference in pain scores from the baseline to 12 weeks after the cessation of treatment demonstrated a small significant difference in favor of the group receiving exercise only (mean difference= 14.7 mm). There were no significant differences between groups in any other variable. Limitations. It was not possible to mask therapists or participants to group allocation. Diagnostic tests were not used on participants to determine specific shoulder pathology. Conclusions. The addition of soft tissue massage to an exercise program for the shoulder conferred no additional benefit for improving pain, disability, or range of motion in people with nonspecific shoulder pain. [ABSTRACT FROM AUTHOR]

Background: Preventing gambling harm has become a policy priority in many European countries. Adverse consequences related to problem gambling are well known, but few studies have analyzed gambling-related harm in detail in general population samples. We determined the extent and distribution of gambling harm in Finland, as assessed by the Problem Gambling Severity Index (PGSI), and analyzed gambling involvement, demographics and their association with various types of harm. Methods: A nationwide telephone survey was conducted among 4484 Finns aged 15-74 years in 2011-12. Gambling-related harms were based on the nine-item PGSI. Gambling involvement was measured by gambling frequency and weekly average gambling expenditure. Associations among harms, demographics and gambling involvement were examined in logistic regression. Results: During the previous year, 13% of respondents experienced at least one gambling-related harm (males 18.1%, females 7.2%). The four commonest harms were ‘chasing losses' (8.6%), ‘escalating gambling to maintain excitement' (3.1%), ‘betting more than could afford to lose’ (2.8%), and ‘feeling guilty' (2.6%). The harm profile in descending order was the same for both genders but differed in prevalence. Young age (<25 years) was associated with increased likelihood of reporting harms. Both monthly and weekly gambling and spending over €21 per week on gambling were related to the harms. Conclusions: Our results provide support for the public health approach to gambling: harms were reported even at low gambling frequency-expenditure levels. In addition to the high-risk approach, adopting a population-level approach to preventing gambling harm could shift the population distribution of harm in a lower direction. [ABSTRACT FROM AUTHOR]

In this study, we compared the relationships of body mass index (BMI) and body adiposity index (BAI) with body fat percentage (BF%) in a Caucasian, European population. BF% was measured by dual-energy x-ray absorptiometry in a population-based cross-sectional study of 5,193 middle-aged (47–49 years) and elderly (71–74 years) men and women from the Hordaland Health Study in western Norway from 1997 to 1999. In the total population, the correlation between BAI and BF% was stronger (r = 0.78) than the correlation between BMI and BF% (r = 0.56) with similar results in the middle-aged and elderly groups. However, in men and women separately, BMI was a better correlate of BF% (for men, r = 0.76; for women, r = 0.81) than was BAI (for men, r = 0.57; for women, r = 0.72). BMI was also a better correlate of BF% than was BAI assessed by partial correlations adjusted for sex (for BMI-BF%, r = 0.79; for BAI-BF%, r = 0.67). Bland-Altman plots and BF%-stratified analyses showed that BAI tended to overestimate BF% in lean subjects and to underestimate it in those with higher proportions of body fat, but that it predicted BF% well for those whose BMI was in a normal range. At the individual level and in population studies adjusted for sex, BMI outperforms BAI as a predictor of BF%. [ABSTRACT FROM PUBLISHER]

Hookah tobacco smoking is increasing among US college students, including those who would not otherwise use tobacco. Part of hookah’s appeal is attributed to the perception that hookah is less harmful than cigarettes. The aims of this study were to assess knowledge of harmful exposures associated with hookah smoking relative to cigarette smoking and to determine associations between this knowledge and hookah smoking outcomes. Students (N = 852) at the University of Florida were randomly sampled via e-mail to obtain information on demographics, hookah smoking behavior and knowledge of five exposures (e.g. tar and nicotine). Multivariable logistic regression models assessed independent associations between knowledge and hookah smoking outcomes. Of the five factual knowledge items asked, 475 (55.8%) of the respondents answered none correctly. In multivariable models, correct responses to any knowledge items were not associated with lower odds of hookah smoking or susceptibility to hookah smoking in the future. Although college students are largely unaware of the toxicant exposures associated with hookah smoking, there is little association between knowledge and hookah smoking behavior. [ABSTRACT FROM PUBLISHER]

Background. Early discontinuation of adjuvant endocrine therapy may affect the outcome of treatment in breast cancer patients. The aim of this study was to assess age-specific persistence and age-specific survival outcome based on persistence status. Methods. Patients enrolled in the Tamoxifen Exemestane Adjuvant Multinational trial were included. Nonpersistence was defined as discontinuing the assigned endocrine treatment within 1 year of follow-up because of adverse events, intercurrent illness, patient refusal, or other reasons. Endpoints were the breast cancer-specific and overall survival times. Analyses were stratified by age at diagnosis (<65 years, 65-74 years, ≥75 years). Results. Overall, 3,142 postmenopausal breast cancer patients were included: 1,682 were aged <65 years, 951 were aged 65-74 years, and 509 were aged ≥75 years. Older age was associated with a higher proportion of nonpersistence within 1 year of follow-up. In patients aged<65 years, nonpersistent patients had lower breast cancer- specific and overall survival probabilities. In patients aged 65-74 years and patients aged ≥75 years, the survival times of persistent and nonpersistent patients were similar. Conclusion. Nonpersistence within 1 year of follow-up was associated with lower breast cancer-specific and overall survival probabilities in patients aged <65 years, but it was not associated with survival outcomes in patients aged 65-74 years or in patients aged>75 years. These results suggest that extrapolation of outcomes from a young to an elderly breast cancer population may be insufficient and urge age-specific breast cancer studies. [ABSTRACT FROM AUTHOR]

Background. The Stair Climb Power Test (SCPT) is a functional test associated with leg muscle power in older people. Objective. The purposes of this study were to compare the results of the SCPT in people with chronic obstructive pulmonary disease (COPD) and people who were healthy and to explore associations of the SCPT with muscle strength (force-generating capacity) and functional performance. Design. The study was a cross-sectional investigation. Methods. Twenty-one people with COPD and a predicted mean (SD) percentage of forced expiratory volume in 1 second of 47.2 (12.9) and 21 people who were healthy and matched for age, sex, and body mass were tested with the SCPT. Knee extensor and flexor muscle torque was assessed with an isokinetic dynamometer. Functional performance was assessed with the Timed "Up & Go" Test (TUG) and the Six-Minute Walk Test (6MWT). Results. People with COPD showed lower values on the SCPT (28%) and all torque measures (~ 32%), except for eccentric knee flexor muscle torque. In people with COPD, performance on the TUG and 6MWT was lower by 23% and 28%, respectively. In people with COPD, the SCPT was moderately associated with knee extensor muscle isometric and eccentric torque (≥r .46) and strongly associated (r = .68) with the 6MWT. In people who were healthy, the association of the SCPT with knee extensor muscle torque tended to be stronger (r≥.66); however, no significant relationship between the SCPT and measures of functional performance was found. Limitations. The observational design of the study and the use of a relatively small convenience sample limit the generalizability of the findings. Conclusions. The SCPT is a simple and safe test associated with measures of functional performance in people with COPD. People with COPD show deficits on the SCPT. However, the SCPT is only moderately associated with muscle torque and thus cannot be used as a simple surrogate for muscle strength in people with COPD. [ABSTRACT FROM AUTHOR]

We propose a new method to construct confidence intervals for quantities that are associated with a stationary time series, which avoids direct estimation of the asymptotic variances. Unlike the existing tuning-parameter-dependent approaches, our method has the attractive convenience of being free of any user-chosen number or smoothing parameter. The interval is constructed on the basis of an asymptotically distribution-free self-normalized statistic, in which the normalizing matrix is computed by using recursive estimates. Under mild conditions, we establish the theoretical validity of our method for a broad class of statistics that are functionals of the empirical distribution of fixed or growing dimension. From a practical point of view, our method is conceptually simple, easy to implement and can be readily used by the practitioner. Monte Carlo simulations are conducted to compare the finite sample performance of the new method with those delivered by the normal approximation and the block bootstrap approach. [ABSTRACT FROM AUTHOR]

Fluorescence curves are useful for monitoring changes in photosynthesis activity. Various summary measures have been used to quantify differences among fluorescence curves corresponding to different treatments, but these approaches may forfeit valuable information. As each individual fluorescence curve is a functional observation, it is natural to consider a functional regression model. The proposed model consists of a nonparametric component capturing the general form of the curves and a semiparametric component describing the differences among treatments and allowing comparisons of treatments. Several graphical model-checking approaches are introduced. Both approximate, asymptotic confidence intervals as well as simulation-based confidence intervals are available. Analysis of data from a crop experiment using the proposed model shows that the salient features in the fluorescence curves are captured adequately. The proposed functional regression model is useful for analysis of high throughput fluorescence curve data from regular monitoring or screening of plant growth. [ABSTRACT FROM AUTHOR]

A small literature discusses locally most powerful rank tests when only a fraction of treated subjects respond to treatment. The ranks used in these tests are very different from conventional ranks, being relatively flat for low responses and then rising steeply, and the associated tests are much more powerful than conventional rank tests when, indeed, only a small fraction of treated subjects exhibit dramatic responses. Because the tests are derived from considerations of local power, they do not yield a plausible family of models for effect, and therefore they do not yield confidence intervals for the magnitude of effect formed by inverting the tests. There is a similarity between these tests and another family of tests, originally motivated by different considerations involving peak performance in small subsets. Exploiting this similarity, a method for obtaining confidence statements is proposed. In the case of observational studies, sensitivity to unobserved bias from nonrandom assignment of treatments is also examined. Two examples are used as illustrations: (i) a study of smoking during pregnancy and its effects on birth weight, in which smokers are matched to six controls, and (ii) a matched pair study of damage to DNA among workers at aluminum production plants. [ABSTRACT FROM AUTHOR]

This article considers the problem of comparing several treatments (dose levels, interventions, etc.) with the best, where the best treatment is unknown and the treatments are ordered in some sense. Order relations among treatments often occur quite naturally in practice. They may be ordered according to increasing risks, such as tolerability or safety problems with increasing dose levels in a dose–response study, for example. We tackle the problem of constructing a lower confidence bound for the smallest index of all treatments being at most marginally less effective than the (best) treatment having the largest effect. Such a bound ensures at confidence level 1 −α that all treatments with lower indices are relevantly less effective than the best competitor. We derive a multiple testing strategy that results in sharp confidence bounds. The proposed lower confidence bound is compared with those derived from other testing strategies. We further derive closed-form expressions for power and sample size calculations. Finally, we investigate several real data sets to illustrate various applications of our methods. [ABSTRACT FROM AUTHOR]

In this article, we provide a method of estimation for the treatment effect in the adaptive design for censored survival data with or without adjusting for risk factors other than the treatment indicator. Within the semiparametric Cox proportional hazards model, we propose a bias-adjusted parameter estimator for the treatment coefficient and its asymptotic confidence interval at the end of the trial. The method for obtaining an asymptotic confidence interval and point estimator is based on a general distribution property of the final test statistic from the weighted linear rank statistics at the interims with or without considering the nuisance covariates. The computation of the estimates is straightforward. Extensive simulation studies show that the asymptotic confidence intervals have reasonable nominal probability of coverage, and the proposed point estimators are nearly unbiased with practical sample sizes. [ABSTRACT FROM AUTHOR]

In experiments involving many variables, investigators typically use multiple comparisons procedures to determine differences that are unlikely to be the result of chance. However, investigators rarely consider how the magnitude of the greatest observed effect sizes may have been subject to bias resulting from multiple testing. These questions of bias become important to the extent investigators focus on the magnitude of the observed effects. As an example, such bias can lead to problems in attempting to validate results, if a biased effect size is used to power a follow-up study. An associated important consequence is that confidence intervals constructed using standard distributions may be badly biased. A bootstrap approach is used to estimate and adjust for the bias in the effect sizes of those variables showing strongest differences. This bias is not always present; some principles showing what factors may lead to greater bias are given and a proof of the convergence of the bootstrap distribution is provided. [ABSTRACT FROM AUTHOR]

The annual percent change (APC) is often used to measure trends in disease and mortality rates, and a common estimator of this parameter uses a linear model on the log of the age-standardized rates. Under the assumption of linearity on the log scale, which is equivalent to a constant change assumption, APC can be equivalently defined in three ways as transformations of either (1) the slope of the line that runs through the log of each rate, (2) the ratio of the last rate to the first rate in the series, or (3) the geometric mean of the proportional changes in the rates over the series. When the constant change assumption fails then the first definition cannot be applied as is, while the second and third definitions unambiguously define the same parameter regardless of whether the assumption holds. We call this parameter the percent change annualized (PCA) and propose two new estimators of it. The first, the two-point estimator, uses only the first and last rates, assuming nothing about the rates in between. This estimator requires fewer assumptions and is asymptotically unbiased as the size of the population gets large, but has more variability since it uses no information from the middle rates. The second estimator is an adaptive one and equals the linear model estimator with a high probability when the rates are not significantly different from linear on the log scale, but includes fewer points if there are significant departures from that linearity. For the two-point estimator we can use confidence intervals previously developed for ratios of directly standardized rates. For the adaptive estimator, we show through simulation that the bootstrap confidence intervals give appropriate coverage. [ABSTRACT FROM AUTHOR]

This article develops methods for stratified analyses of additive or multiplicative causal effect on binary outcomes in randomized trials with noncompliance. The methods are based on a weighted estimating function for an unbiased estimating function under randomization in each stratum. When known weights are used, the derived estimator is a natural extension of the instrumental variable estimator for stratified analyses, and test-based confidence limits are solutions of a quadratic equation in the causal parameter. Optimal weights that maximize asymptotic efficiency incorporate variability in compliance aspects across strata. An assessment based on asymptotic relative efficiency shows that a substantial enhancement in efficiency can be gained by using optimal weights instead of conventional ones, which do not incorporate the variability in compliance aspects across strata. Application to a field trial for coronary heart disease is provided. [ABSTRACT FROM AUTHOR]

We consider a very general class of empirical discrepancy statistics that includes the Cressie–Read discrepancy statistics and, in particular, the empirical likelihood ratio statistic. Higher-order asymptotics for expected lengths of associated confidence intervals are investigated. An explicit formula is worked out and its use for comparative purposes is discussed. It is seen that the empirical likelihood ratio statistic, which enjoys interesting second-order power properties, loses much of its edge under the present criterion. [ABSTRACT FROM AUTHOR]

Consider a sequential test applied to two streams of binary responses in a comparative clinical trial. After the completion of such a trial Woodroofe's (1992) technique for accurate confidence interval estimation for a treatment difference can be applied. In this paper the technique is extended to provide confidence intervals for the individual absolute success probabilities of the two treatments in the trial, for which no current methodology exists. Accuracy is explored by simulation of coverage probabilities and individual confidence limit probabilities. The simulations concern a triangular test and an O'Brien & Fleming test. [ABSTRACT FROM AUTHOR]

The article offers information regarding problems faced while sample size estimation. Various methods of sample size selections include recourse to local tradition, ready availability of data, unaided intuition, usually called 'experience' and negotiation. Steps involved in construction a confidence interval plot, hypothesis testers and parameter fitters, constructing a confidence interval plot and selecting a sample size are informed about. Besides the issue of subjectivity, another consideration involved in the use of CI plots is the fact that CIs only take account of sampling errors.

When analyzing a 2 × 2 table, the two-sided Fisher's exact test and the usual exact confidence interval (CI) for the odds ratio may give conflicting inferences; for example, the test rejects but the associated CI contains an odds ratio of 1. The problem is that the usual exact CI is the inversion of the test that rejects if either of the one-sided Fisher's exact tests rejects at half the nominal significance level. Further, the confidence set that is the inversion of the usual two-sided Fisher's exact test may not be an interval, so following Blaker (2000, Confidence curves and improved exact confidence intervals for discrete distributions. Canadian Journal of Statistics 28, 783–798), we define the “matching” interval as the smallest interval that contains the confidence set. We explore these 2 versions of Fisher's exact test as well as an exact test suggested by Blaker (2000) and provide the R package exact2 ×2 which automatically assigns the appropriate matching interval to each of the 3 exact tests. [ABSTRACT FROM PUBLISHER]

We investigate data tapering in two formulations of empirical likelihood for time series. One empirical likelihood is formed from tapered data blocks in the time domain and a second is based on the tapered periodogram in the frequency domain. Limiting distributions are provided for both empirical likelihood versions under tapering. Theoretical and simulation evidence indicates that a data taper improves the coverage accuracy of empirical likelihood confidence intervals for time series parameters, such as means and correlations. [ABSTRACT FROM AUTHOR]

We propose a new method, to construct confidence intervals for spectral mean and related ratio statistics of a stationary process, that avoids direct estimation of their asymptotic variances. By introducing a bandwidth, a self-normalization procedure is adopted and the distribution of the new statistic is asymptotically nuisance-parameter free. The bandwidth is chosen using information criteria and a moving average sieve approximation. Through a simulation study, we demonstrate good finite sample performance of our method when the sample size is moderate, while a comparison with an empirical likelihood-based method for ratio statistics is made, confirming a wider applicability of our method. [ABSTRACT FROM AUTHOR]

Test statistics from the weighted log-rank class are commonly used to compare treatment with control when there is right censoring. This paper uses saddlepoint methods to determine mid-p-values from the null permutation distributions of tests from the weighted log-rank class. Analytical saddlepoint computations replace the permutation simulations and provide mid-p-values that are virtually exact for all practical purposes. The speed of these saddlepoint computations makes it practicable to invert the weighted log-rank tests to determine nominal 95% confidence intervals for the treatment effect with right-censored data. Such analytical inversions lead to permutation confidence intervals that are easily computed and virtually identical to the exact intervals that would normally require massive amounts of simulation. [ABSTRACT FROM AUTHOR]