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  • SAGE Publications  (2)
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  • SAGE Publications  (2)
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  • 1
    Online Resource
    Online Resource
    SAGE Publications ; 2014
    In:  Statistical Methods in Medical Research Vol. 23, No. 3 ( 2014-06), p. 218-243
    In: Statistical Methods in Medical Research, SAGE Publications, Vol. 23, No. 3 ( 2014-06), p. 218-243
    Abstract: The Cochran–Armitage (CA) test is commonly used in both epidemiology and genetics to test for linear trend in two-way tables with a binary outcome. There has been increasing interest in the power and size of the test and in determination of sample size, especially when there is potential misclassification in the ‘exposure’ category. This article provides a unified approach to determination of the power function over different sampling strategies (fixed overall sample size or fixed marginal sample sizes) and allowing for misclassification in one or both variables. The misclassification may be either differential or non-differential. In addition to the standard CA test, results are also given which provide some insight into the performance of the modified CA test, which utilizes a standard error obtained without invoking the null hypothesis. Even without misclassification, some new expressions are also obtained for determining power with a fixed overall sample size. Numerical illustrations are presented with an emphasis on the more commonly occurring problem of misclassification in the exposure category.
    Type of Medium: Online Resource
    ISSN: 0962-2802 , 1477-0334
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2014
    detail.hit.zdb_id: 2001539-2
    detail.hit.zdb_id: 1136948-6
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  • 2
    Online Resource
    Online Resource
    SAGE Publications ; 1997
    In:  Scandinavian Journal of Social Medicine Vol. 25, No. 1 ( 1997-03), p. 33-38
    In: Scandinavian Journal of Social Medicine, SAGE Publications, Vol. 25, No. 1 ( 1997-03), p. 33-38
    Abstract: The three main objectives of this study were to estimate the proportion of the Norwegian population with experience of homosexual behaviour, to study the degree of change in sexual practices among homosexual men during a 5-year period and to study the degree of change in sexual practices reported by HIV positive homosexual men from before to after awareness of HIV-positivity. The data comes from two questionnaire surveys (in 1987 and 1992) of sexual behaviour in the general population of Norway and a questionnaire study of sexual behaviour before and after awareness of HIV-positivity among HIV-positive homosexual men taking part in a cohort study starting in 1988 (the Oslo HIV cohort study). Estimation of the proportion of subjects with homosexual experience was made as well as a trend analysis of the number of male sexual partners per year, number of intercourses per month, condom use and anal sex. Among men aged 18 to 60 from the general population, 3.8% reported homosexual practice during lifetime and 1.2% during the past 3 years. Among women, the same percentages were 3.1 and 1.0. In the surveys, the number of male partners per year decreased significantly for men with current homosexual experience from a yearly median of 1.0 in 1987 to 0.3 in 1992 ( p = 0.02). Among HIV-positives, the number of male partners decreased from a yearly median of 4.3 before to 1.6 after awareness of HIV-seropositivity ( p 〈 0.01). Among HIV-positives, a significant increase in the use of condoms, a decrease in the number of intercourses and a decrease in the frequency of anal sex was found. The results show that some changes in sexual practice may have occurred among homosexual men in general in the period from 1987 to 1992, and that more significant changes may have occurred for HIV-positive men. The present data do not support other findings of a relapse to more unsafe sex, but suggest that there is still a need to keep modifying behaviour in order to stop the spread of HIV among men who have sex with other men.
    Type of Medium: Online Resource
    ISSN: 0300-8037
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1997
    detail.hit.zdb_id: 2027122-0
    detail.hit.zdb_id: 2253902-5
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