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This paper, extracted from National Research Council (2015), summarizes the findings and recommendations from a recent report from the Panel on Reliability Growth Methods for Defense Systems, operating under the auspices of the Committee on National Statistics (CNSTAT) within the National Research Council (NRC). The report offers recommendations to improve defense system reliability throughout the sequence of stages that comprise U.S. Department of Defense (DoD) acquisition processes -- beginning with the articulation of requirements for new systems and ending with feedback mechanisms that document the reliability experience of deployed systems. A number of these recommendations are partially or fully embraced by current DoD directives and practice, particularly with the advent of recent DoD initiatives that elevate the importance of design for reliability techniques, reliability growth testing, and formal reliability growth modeling. The report supports the many recent steps taken by DoD, building on these while addressing associated engineering and statistical issues. The report provides a self-contained rendition of reliability enhancement proposals, recognizing that current DoD guides and directives have not been fully absorbed or consistently applied and are subject to change. [ABSTRACT FROM AUTHOR]

Shows how to plan two-factor accelerated life tests (ALTs) with censored data. C optimality; D optimality; Design of experiments; Life data; Lognormal distribution; Reliability; Test planning; Weibull distribution; Review of literature.

Extends the maximum likelihood theory for test planning to the nonconstant model and presents test plans for a large range of practical testing situations concerning optimum accelerated life tests. Related work; Model assumptions and test stresses; Model standardization and reparameterization; Compromise test plans and comparisons.

Failures of solid-state electronic components are often caused by manufacturing defects. Typically, a small proportion of the manufactured components has one or more defects that cannot be detected in a simple inspection but that will eventually cause the component to fail. If a component has no such defects, the probability that it will fail under carefully controlled conditions is virtually 0. By assuming a time-to-failure distribution for the units that are susceptible to failure from manufacturing defects, laboratory life tests of limited duration can be used to estimate the proportion of units that have such defects and the parameters of the assumed time-to-failure distribution of the defective subpopulation. The purpose of this article is to outline methods for analyzing life test data from life tests for "limited-failure" populations. Applications are described and a numerical example is included. [ABSTRACT FROM AUTHOR]

SUMMARY This paper suggests a conditional sequential test for the equality of two binomial proportions. The test is a sequential analog of Fisher's exact test. A numerical example is given and the new test is compared with other tests, both sequential and fixed sample size. The results indicate that the conditional test is easy to use and that it has desirable test properties, even when truncated after a prespecified number of observations. An appendix shows how to compute the exact properties of the test. [ABSTRACT FROM AUTHOR]

Previous work on planning accelerated life test plans for the Weibull and lognormal distributions has concentrated on optimum test plans that minimize the variance of some specified estimator. However, these test plans use tests at only two levels of stress and, thus, have serious practical limitations. This article compares optimum test plans and some compromise test plans with respect to additional criteria including (a) the ability to detect departures from the assumed stress-life relationship and (b) robustness to departures from the assumptions used in determining the plans. The comparisons are based on the large sample properties of maximum likelihood estimators, and the test plans are compared over a range of practical testing situations. The comparisons suggest some general rules for planning accelerated life tests. [ABSTRACT FROM AUTHOR]

Comments on J.F. Lawless's (1983) study of the application of statistical methods in reliability problems. Reasons for collecting life data; Issues to consider with respect to bringing statistical methods to practice; Areas requiring additional development of theory and practice.

Methods are given for constructing, from past sample data, prediction intervals (i) to contain the ratio of the variances of future samples from two normal distributions and (ii) to contain the ratio of the means from future samples from two exponential distributions. Such intervals are required, for example, when a producer wishes to predict the results of a future test, to be conducted by a consumer or regulatory agency, to compare its product with a competitor's. A new tabulation of percentage points of the distribution of two independent F ratios to obtain such intervals is provided; this extends existing tabulations. [ABSTRACT FROM AUTHOR]

This note presents a table of the large sample covariance matrix of the maximum likelihood (ML) estimates of parameters of a smallest extreme value distribution. The table can be used to obtain approximate large-sample confidence intervals when a Weibull (or smallest extreme value distribution) is fitted by ML to singly censored data. Use of the table is illustrated with such data on the life of locomotive controls. [ABSTRACT FROM AUTHOR]

This paper is concerned with the optimum allocation of test units to overstress conditions when it is desired to estimate the survival probability at a design condition with a low expected failure probability. The criterion is that of minimizing the large sample variance; a logistic model is assumed. Expressions and charts for allocating test units to the accelerated stresses are provided and procedures for determining the stresses when these are not all specified are given. The gain in efficiency from using these plans versus testing exclusively at the design condition is analyzed. The requirement for some testing at the design stress and at an intermediate stress is also considered. [ABSTRACT FROM AUTHOR]

Focuses on the use computer program for evaluating and comparing experimental designs and applications. Determination of alternative properties and unbalanced test plans; Development of computer program EXPLOR for the purpose; Uses of the programs.

The author reflects on the role of architecture and design excellence to the society. He believes that architecture is a public endeavor as it involves design professionals, clients, users and the community. He points out that threats to design excellence are dependent on the economics of the construction process, democracy of the building process and indifference. The author concludes that excellence in architecture is in the consolidation of acknowledgement of the needs of the public, climate, site, craftsmanship and present technology conditions.

In a previous paper [3], the authors presented large sample optimum accelerated test plans to estimate the survival probability at a design stress assuming a linear logistic model, i.e. a linear relationship between stress and the log survival odds at that stress. The optimum plans required testing at two accelerated stresses with a larger allocation of units assigned to the lower of the two stresses. In practice, however, it is often desirable to conduct the accelerated tests at more than two stresses and/or use equal or otherwise prespecified allocation. In this paper we compare the large sample variance of each often such non-optimum test plans (and also that of testing exclusively at the design stress) with that of the optimum plan under a variety of conditions. [ABSTRACT FROM AUTHOR]

Features Tseries, a computer program for Box-Jenkins analysis of univariate time series data. Accomplishment of input through series of simple and compact command; Suitability of the series on practical applications and students hands-on experience; Performance capabilities.

Describes a program for assessing experimental design properties of the computer program called EXPLOR. Construction of the model based on proposed design points and assumed statistical model; Calculation of various design properties; Application and features of EXPLOR.

Presents a user-oriented computer program (CENSOR) to perform probability plotting, maximum likelihood estimation for censored and group-censored data. Experimentation on life data analysis; Similarity of CENSOR to MINITAB statistical computing system; List of features and outputs by CENSOR.

Background: Knowing the approximate number of women of reproductive age (ie, 15-49 years) who are pregnant at a point in time in the United States can aid in emergency preparedness resource allocation. The Centers for Disease Control and Prevention (CDC) released a pregnancy estimator toolkit in 2012, which could be used to estimate the number of pregnant people in a geographic area at a point in time. This original toolkit did not account for pregnancy losses before 20 weeks of gestation; however, an updated toolkit released by the CDC in May 2024 uses a ratio of live births to estimate the number of pregnancy losses before 20 weeks at a point in time for improved estimation of total pregnant people at a point in time., Instrument: We used the CDC's updated reproductive health tool, "Estimating the Number of Pregnant Women in a Geographic Area.", Experience: Using publicly available data for 2020, we gathered the necessary input values, including total births, fetal deaths, and induced abortions, and applied the equation available in the CDC toolkit to estimate the number of pregnant people in the United States at any point in time in 2020., Conclusion: In 2020, there were 75,582,028 women of reproductive age in the United States, and we estimate that approximately 2,962,052 or 3.9% of women of reproductive age were pregnant at any point in time in the United States., Competing Interests: Financial Disclosure The authors did not report any potential conflicts of interest., (Copyright © 2024 by the American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.)

Objectives: Public health emergencies can elevate the risk for intimate partner violence (IPV). Our objectives were 2-fold: first, to assess the prevalence of physical IPV and increased aggression from a husband or partner that occurred during pregnancy and was perceived to be due to the COVID-19 pandemic; second, to examine associations between these experiences and (1) COVID-19-related stressors and (2) postpartum outcomes., Methods: We used data from the Pregnancy Risk Assessment Monitoring System that were collected in 29 US jurisdictions among individuals with a live birth in 2020. We estimated the prevalence of violence during pregnancy by demographic characteristics and COVID-19-related stressors. We calculated adjusted prevalence ratios (APRs) to examine associations of physical IPV or increased aggression with COVID-19-related stressors, postpartum outcomes, and infant birth outcomes., Results: Among 14 154 respondents, 1.6% reported physical IPV during pregnancy, and 3.1% reported increased aggression by a husband or partner due to the COVID-19 pandemic. Respondents experiencing any economic, housing, or childcare COVID-19-related stressors reported approximately twice the prevalence of both types of violence as compared with those without COVID-19-related stressors. Physical IPV and increased aggression were associated with a higher prevalence of postpartum depressive symptoms (APRs, 1.73 and 2.28, respectively) and postpartum cigarette smoking (APRs, 1.74 and 2.19). Physical IPV was associated with a lower prevalence of attending postpartum care visits (APR, 1.84)., Conclusions: Our findings support the need for ongoing efforts to prevent IPV during pregnancy and to ensure the availability of resources during public health emergencies., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

This report describes opportunities to address emergency preparedness to incorporate the needs of pregnant and postpartum populations. This report briefly summarizes data on the impacts of weather and climate disasters on maternal and infant health and outlines opportunities for individuals, health care providers, and public health practitioners to increase capacity to prepare for these occurrences, which are becoming more frequent and costly. Specific resources from the U.S. Centers for Disease Control and Prevention's Division of Reproductive Health are shared to support individual preparedness, communication of disaster safety messages, and emergency preparedness planning capacity among health care providers and health departments.

Objective: We investigated maternal COVID-19 related experiences during delivery hospitalizations, and whether experiences differed by maternal race and ethnicity., Study Design: Data from the Pregnancy Risk Assessment Monitoring System among women with live births between April-December 2020 were used. Adjusted prevalence ratios (aPR) and 95% confidence intervals (CI) estimated associations between maternal race and ethnicity and COVID-19 related delivery experiences., Results: Among 12,879 women, 3.6% reported infant separation and 1.8% reported not being allowed support persons. Compared with non-Hispanic White women, American Indian/Alaska Native (AI/AN) (aPR = 2.7; CI: 1.2-6.2), Hispanic (aPR = 2.2; CI: 1.5-3.1), non-Hispanic Black (aPR = 2.4; CI: 1.7-3.6), and non-Hispanic Asian (aPR = 2.8; CI: 1.6-4.9) women reported more infant separation due to COVID-19. Not being allowed support persons was more common among AI/AN (aPR = 5.2; CI: 1.8-14.8) and non-Hispanic Black (aPR = 2.3; CI: 1.3-4.1) women., Conclusions: COVID-19 related delivery hospitalization experiences were unequally distributed among racial and ethnic minorities., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Pregnant, postpartum, and lactating people, and infants have unique needs during public health emergencies, including nuclear and radiological incidents. This report provides information on the CDC Division of Reproductive Health's emergency preparedness and response activities to address the needs of women of reproductive age (aged 15-49 years), people who are pregnant, postpartum, or lactating, and infants during a radiation emergency. Highlighted preparedness activities include: (1) development of a quick reference guide to inform key questions about pregnant, postpartum, and lactating people, and infants during radiation emergencies; and (2) exercising the role of reproductive health experts during nuclear and radiological incident preparedness activities.

The objective of this analysis was to assess the associations between pandemic-related stressors and feeling more anxious/depressed, among women with a live birth. We analyzed data from the Pregnancy Risk Assessment Monitoring System (PRAMS) COVID-19 maternal experiences supplement, implemented in 29 U.S. jurisdictions from October 2020-June 2021, among women with a live birth during April-December 2020. We examined stressors by type (economic, housing, childcare, food insecurity, partner, COVID-19 illness) and score (number of stressor types experienced [none, 1-2, 3-4, or 5-6]). Outcomes were feeling 1) more anxious and 2) more depressed than usual due to the pandemic. We calculated adjusted prevalence ratios estimating associations between stressors and outcomes. Among 12,525 respondents, half reported feeling more anxious and 28% more depressed than usual. The prevalence of stressor types was 50% economic, 41% childcare, 18% partner, 17% food insecurity, 12% housing, and 10% COVID-19 illness. Respondents who experienced partner stressors (anxious aPR: 1.81, 95% CI: 1.73-1.90; depressed aPR: 3.01, 95% CI: 2.78-3.25) and food insecurity (anxious aPR: 1.79, 95% CI: 1.71-1.88; depressed aPR: 2.32, 95% CI: 2.13-2.53) had the largest associations with feeling more anxious and depressed than usual. As stressor scores increased, so did the aPRs for feeling more anxious and more depressed due to the pandemic. COVID-19 stressors, not COVID-19 illness, were found to be significantly associated with feeling more anxious and depressed. Pregnant and postpartum women might benefit from access to supports and services to address pandemic-related stressors/social-determinants and feelings of anxiety and depression., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

We report on five SARS-CoV-2 congregate setting outbreaks at U.S. Operation Allies Welcome Safe Havens/military facilities. Outbreak data were collected, and attack rates were calculated for various populations. Even in vaccinated populations, there was rapid spread, illustrating the importance of institutional prevention and mitigation policies in congregate settings., (© 2023 Wiley Periodicals LLC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Purpose: To measure associations of area-level racial and economic residential segregation with severe maternal morbidity (SMM)., Methods: We conducted a retrospective cohort study of births at two Philadelphia hospitals between 2018 and 2020 to analyze associations of segregation, quantified using the Index of Concentration at the Extremes (ICE), with SMM. We used stratified multivariable, multilevel, logistic regression models to determine whether associations of ICE with SMM varied by self-identified race or hospital catchment., Results: Of the 25,979 patients (44.1% Black, 35.8% White), 1381 (5.3%) had SMM (Black [6.1%], White [4.4%]). SMM was higher among patients residing outside (6.3%), than inside (5.0%) Philadelphia (P < .001). Overall, ICE was not associated with SMM. However, ICE race (higher proportion of White vs. Black households) was associated with lower odds of SMM among patients residing inside Philadelphia (aOR 0.87, 95% CI: 0.80-0.94) and higher odds outside Philadelphia (aOR 1.12, 95% CI: 0.95-1.31). Moran's I indicated spatial autocorrelation of SMM overall (P < .001); when stratified, autocorrelation was only evident outside Philadelphia., Conclusions: Overall, ICE was not associated with SMM. However, higher ICE race was associated with lower odds of SMM among Philadelphia residents. Findings highlight the importance of hospital catchment area and referral patterns in spatial analyses of hospital datasets., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Heather H. Burris reports financial support was provided by the National Institutes of Health., (Copyright © 2023 Elsevier Inc. All rights reserved.)

We report healthcare provider attitudes and practices on emergency preparedness counseling for women of reproductive age (WRA), including pregnant, postpartum, and lactating women (PPLW), for disasters and weather emergencies. DocStyles is a web-based panel survey of primary healthcare providers in the United States. During March 17-May 17, 2021, obstetricians-gynecologists, family practitioners, internists, nurse practitioners, and physician assistants were asked about the importance of emergency preparedness counseling, level of confidence, frequency, barriers to providing counseling, and preferred resources to support counseling among WRA and PPLW. We calculated frequencies of provider attitudes and practices, and prevalence ratios with 95% CIs for questions with binary responses. Among 1503 respondents (family practitioners (33%), internists (34%), obstetrician-gynecologists (17%), nurse practitioners (8%), and physician assistants (8%)), 77% thought emergency preparedness was important, and 88% thought counseling was necessary for patient health and safety. However, 45% of respondents did not feel confident providing emergency preparedness counseling, and most (70%) had never talked to PPLW about this topic. Respondents cited not having time during clinical visits (48%) and lack of knowledge (34%) as barriers to providing counseling. Most respondents (79%) stated they would use emergency preparedness educational materials for WRA, and 60% said they were willing to take an emergency preparedness training. Healthcare providers have opportunities to provide emergency preparedness counseling; however, many have not, noting lack of time and knowledge as barriers. Emergency preparedness resources combined with training may improve healthcare provider confidence and increase delivery of emergency preparedness counseling., Competing Interests: Declaration of Competing Interest The authors declare they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Inc.)