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Background Since the outbreak of the novel coronavirus disease (COVID-19) in December 2019, the coronavirus has spread all over the world at an unprecedented rate. The transmissibility of the coronavirus from asymptomatic patients to healthy individuals has received enormous attention. An important study using COVID-19 data from the city of Ningbo, China, was carried out to estimate and compare the transmission rates of the coronavirus by the symptomatic and asymptomatic patients. However, in the original analysis, the usual chi-square tests were unduly used for some contingency tables with small cell counts including zero, which may violate the assumptions for the chi-square test. Objective We reanalyze the data from the city of Ningbo with more appropriate statistical methods to draw more reliable and sound conclusions on the transmission rates of the coronavirus by the symptomatic and asymptomatic patients. Methods We excluded the cases associated with the super-spreader and adopted a more appropriate statistical method, including the permutation test and the Fisher exact test, to reanalyze the COVID-19 data from the city of Ningbo. Results After excluding the cases related to the super-spreader, the Fisher exact test yields a P value of .84, which indicates stronger evidence of no difference in the transmission rates compared with the original analysis. The odds ratio of the coronavirus transmission rates between the symptomatic and asymptomatic patients is 1.2 with a 95% confidence interval 0.5-2.8. Conclusions Through a more in-depth and comprehensive statistical analysis of the Ningbo data, we concluded that there is no difference in the transmission rates of coronavirus between symptomatic and asymptomatic patients.

Slavic verbal aspect is obligatorily morphologically expressed in the infinitive and infinite verbal forms as one of two opposing values: perfective or imperfective. Additionally, Slavic languages also have biaspectual verbs. If no context is provided, the infi nitive of such a verb has the potential to express both aspectual values. In order to achieve greater communicational transparency, however, native speakers sometimes use affi xation to derive overtly aspectually marked verbs from biaspectual verbs. Still, not all biaspectual verbs are equally prone to affixation. Moreover, some aspectologists suggest that the type of aspectual affixation seems to depend on the inner actional properties of a verb, not only in the case of biaspectual verbs but in general. Th at assumption is the starting point for this study of biaspectual verbs and their affixation. This paper addresses the following research question: Do morphologically stable (without any overtly aspectually marked derivatives) and unstable (with overtly aspectually marked derivatives) biaspectual verbs differ on the lexical level, i.e., are their actional properties significantly different? The analysis was conducted on a sample of 38 biaspectual verbs. First, lexical meanings for each analyzed verb were compared and extracted from three dictionaries of contemporary Croatian. Second, a lexical–actional function (actional class) was assigned to each meaning according to a classification proposed within the formal–functional theory of Slavic aspect (Lehmann 1999a, 2009a). In the last step the Fisher exact test was performed. The statistical analysis suggests that the actional properties of morphologically stable and unstable biaspectual verbs differ significantly, U slavenskim je jezicima glagolski aspekt obavezna gramatička kategorija, prisutna u infinitivu kao i u svim ostalim glagolskim oblicima kao jedna od dviju oprečnih vrijednosti: perfektivno – imperfektivno. No osim perfektivnih i imperfektivnih glagola u slavenskim jezicima postoje i dvovidni glagoli. U literaturi se napominje kako infinitiv spomenutih glagola može izraziti obje aspektne vrijednosti, i perfektivnu i imperfektivnu, kao i to da se u kontekstu ostvaruje samo jedna od njih. Međutim, u nekim slučajevima nije baš potpuno jasno koja je aspektna vrijednost ostvarena. Kako bi postigli što veći stupanj komunikacijske jasnoće, izvorni govornici često pribjegavaju afiksaciji dvovidnih glagola pri čemu neki dvovidni glagoli ipak ne podliježu spomenutome procesu. No, kada se govori o aspektnoj afiksaciji općenito, dakle ne samo u kontekstu dvovidnih glagola, svakako treba imati na umu da dio aspektologa tip aspektne afiksacije povezuje s akcionalnim obilježjima (tzv. leksičkim aspektom) glagola. Upravo potonja pretpostavka uzima se kao polazište ovoga rada u kojemu se proučava afiksacija dvovidnih glagola. Točnije govoreći, ovim se radom nastoji odgovoriti na sljedeće istraživačko pitanje: Razlikuju li se akcionalna obilježja morfološki stabilnih dvovidnih glagola (onih koji ne podliježu aspektnoj afiksaciji) i morfološki nestabilnih dvovidnih glagola (onih koji sudjeluju u afiksaciji)? Analiza se provodi na uzorku od 38 dvovidnih glagola. U prvome koraku ispisana su sva pojedina značenja (i varijante značenja) svakoga od analiziranih glagola. U drugome koraku svakome je značenju pripisana leksičko–akcionalna funkcija u skladu s postavkama formalno–funkcionalne teorije slavenskoga aspekta (Lehmann 1999a, 2009a). Posljednji korak uključuje statističku analizu, odnosno primjenu Fisherova testa. Rezultati analize jasno upućuju na to da se akcionalna obilježja stabilnih i nestabilnih dvovidnih glagola značajno razlikuju.

The Chi-Square test (χ 2 test) is a family of tests based on a series of assumptions and is frequently used in the statistical analysis of experimental data. The aim of our paper was to present solutions to common problems when applying the Chi-square tests for testing goodness-of-fit, homogeneity and independence. The main characteristics of these three tests are presented along with various problems related to their application. The main problems identified in the application of the goodness-of-fit test were as follows: defining the frequency classes, calculating the X 2 statistic, and applying the χ 2 test. Several solutions were identified, presented and analyzed. Three different equations were identified as being able to determine the contribution of each factor on three hypothesizes (minimization of variance, minimization of square coefficient of variation and minimization of X 2 statistic) in the application of the Chi-square test of homogeneity. The best solution was directly related to the distribution of the experimental error. The Fisher exact test proved to be the "golden test" in analyzing the independence while the Yates and Mantel-Haenszel corrections could be applied as alternative tests.

In this paper we present a technique to derive rules describing contrast sets. Contrast sets are a formalism to represent groups diferences. We propose a novel approach to describe directional contrasts using rules where the contrasting efect is partitioned into pairs of groups. Our approach makes use of a directional Fisher Exact Test to and significant diferences across groups. We used a Bonferroni within search adjustment to control type I errors and a pruning technique to prevent derivation of non significant contrast set specializations., Thanks to Prof. M. Pazzani for kindly providing the code for the STUCCO algorithm. This work was Supported by Fundacao Ciencia e Tecnologia, Project PFound, Project ProtUnf, FEDER and Programa de Financiamento Plurianual de Unidades de I & D.