The characteristics of crash-involved seat belt non-users in a high use state (Hawaii) are examined in order to better design enforcement and education programs. Using police crash report data over a ...10-year period (1986–1995), we compare belted and unbelted drivers and front seat occupants, who were seriously injured in crashes, in terms of personal (age, gender, alcohol involvement, etc.) and crash characteristics (time, location, roadway factors, etc.). A logistic regression model combined with the spline method is used to analyze and categorize the salient differences between users and non-users. We find that unbelted occupants are more likely to be male, younger, unlicensed, intoxicated and driving pickup trucks versus other vehicles. Moreover, non-users are more likely than users to be involved in speed-related crashes in rural areas during the nighttime. Passengers are 70 times more likely to be unbelted if the driver is also unbelted than passengers of vehicles with belted drivers. While our general findings are similar to other seat belt studies, the contribution of this paper is in terms of a deeper understanding of the relative importance of various factors associated with non-use among seriously injured occupants as well as demonstrating a powerful methodology for analyzing safety problems entailing the categorization of various groups. While the former has implication for seat belt enforcement and education programs, the latter is relevant to a host of other research questions.
In order to clarify the limitations and the effectiveness of filtering-type bulk sampler, a study on precipitation collected by filtering-type bulk and wet-only samplers was performed. At an urban ...site, there was a statistically significant difference between the filtering-type bulk and wet-only samples at a 1% significance level in the pH and major chemical components. At a suburban site, pH, NH
4
+, and nss-Ca
2+ showed a difference at a 1% significance level and NO
3
− at a 5% significance level, but nss-SO
4
2− did not show any difference even at a 5% significance level. At a rural site, although there was a difference in nss-Ca
2+ at a 1% significance level and in pH at a 5% significance level, nss-SO
4
2−, NO
3
−, and NH
4
+ did not show any difference. The attributions of the deposition of gaseous compounds and particulate matter in a filtering-type bulk sampler were estimated to be 32% (nss-SO
4
2−), 46% (NO
3
−), 36% (NH
4
+), and 75% (nss-Ca
2+) at an urban site, 14% (nss-SO
4
2−), 16% (NO
3
−), 27% (NH
4
+), and 42% (nss-Ca
2+) at a suburban site, and 16% (nss-SO
4
2−), 17% (NO
3
−), 19% (NH
4
+), and 47% (nss-Ca
2+) at a rural site. The degree of pollution at a sampling site should be taken into account when using a data set collected with filtering-type bulk samplers.
This paper analyzes small sample properties of several versions of z-tests in multinomial probit models under simulated maximum likelihood estimation. Our Monte Carlo experiments show that z-tests on ...utility function coefficients provide more robust results than z-tests on variance covariance parameters. As expected, both the number of observations and the number of random draws in the incorporated Geweke-Hajivassiliou-Keane (GHK) simulator have on average a positive impact on the conformities between the shares of type I errors and the nominal significance levels. Furthermore, an increase of the number of observations leads to an expected decrease of the shares of type II errors, whereas the number of random draws in the GHK simulator surprisingly has no significant effect in this respect. One main result of our study is that the use of the robust version of the simulated z-test statistics is not systematically more favorable than the use of other versions. However, the application of the z-test statistics that exclusively include the Hessian matrix of the simulated loglikelihood function to estimate the information matrix often leads to substantial computational problems.
9 - Testing hypotheses Joann G. Elmore; Dorothea M.G. Wild; Heidi D. Nelson ...
Jekel's Epidemiology, Biostatistics, Preventive Medicine, and Public Health,
2020
Book Chapter
This chapter is about testing hypotheses using statistical methods.
This chapter contains sections titled:
Statistics and the Scientific Method
Estimation Precision
Power of Z‐Tests
Test for Two Proportions
Power of Chi‐Square Tests
SAS PROC POWER
Efficiency
A presente pesquisa visou constatar as condições afetivo-emocionais em mulheres com síndrome pré-menstrual (SPM), comparadas com outras mulheres sem sintomas pré-menstruais. A amostra foi constituída ...de 43 universitárias, na faixa etária de 18 e 35 anos, distribuídas em dois grupos: Grupo 1, constituído de 25 mulheres com SPM, e Grupo 2 (Controle), de 18 mulheres sem estas disfunções. Foram utilizados como instrumentos a técnica de Zulliger (Z-Teste forma coletiva) e o Inventário de Ansiedade-Traço-Estado - IDATE (Spielberger), e para tratamento estatístico na análise comparativa dos dados o t-Teste para amostras independentes. O nível de significância escolhido foi p < 0.05. Os resultados indicaram que as mulheres do grupo com síndrome pré-menstrual reagem emocionalmente de forma mais intensa e têm tendência à perda de controle emocional em índice maior que as mulheres do grupo sem sintomas pré-menstruais.
A presente pesquisa visou constatar as condições afetivo-emocionais em mulheres com síndrome pré-menstrual (SPM), comparadas com outras mulheres sem sintomas pré-menstruais. A amostra foi constituída ...de 43 universitárias, na faixa etária de 18 e 35 anos, distribuídas em dois grupos: Grupo 1, constituído de 25 mulheres com SPM, e Grupo 2 (Controle), de 18 mulheres sem estas disfunções. Foram utilizados como instrumentos a técnica de Zulliger (Z-Teste forma coletiva) e o Inventário de Ansiedade-Traço-Estado - IDATE (Spielberger), e para tratamento estatístico na análise comparativa dos dados o t-Teste para amostras independentes. O nível de significância escolhido foi p < 0.05. Os resultados indicaram que as mulheres do grupo com síndrome pré-menstrual reagem emocionalmente de forma mais intensa e têm tendência à perda de controle emocional em índice maior que as mulheres do grupo sem sintomas pré-menstruais.
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