![]() The differences might be larger when the "before" values are larger, and smaller when the "before" values are smaller. With some kinds of data, the difference between before and after is not a consistent measure of effect. The paired t test works by analyzing the difference between each pair of values, testing the null hypothesis that the average difference is zero. The Wilcoxon matched-pairs test (nonparametric test of two paired or matched groups) reports the confidence interval of the median of the paired differences, and the Wilcoxon signed rank sum test (nonparametric test to compare a median with a hypothetical median) now reports the confidence interval of the difference between the actual sample median and the hypothetical median. The Wilcoxon test computes the 95% CI of the median.Accordingly, Prism 6 can now report the confidence interval for the difference of two medians. However, if you assume that the two distributions have roughly the same shape, then it is fair to think of the Mann-Whitney test as comparing two medians. That is not precisely correct, as it is possible for two groups to have the same median, but for the Mann-Whitney test to find that the difference between the distribution of ranks among the two groups is statistically significant. The Mann-Whitney test is often described as comparing the median of the two groups. Mann-Whitney tests reports 95% CI of difference between medians.Prism now reports the ratio of median survival times, and its confidence interval, both ways so you can choose which to report. If people in group A have a median survival time three times people in group B, then people in group B have one third the median survival of people in group A.Prism now reports the hazard ratio, and its confidence interval, both ways so you can report the one that makes most sense in your clinical context. If people in group A die at twice the rate of people in group B (HR=2.0), then people in group B die at half the rate of people in group A (HR=0.5).Prism now computes the hazard ratio (HR) by two methods: The logrank method and the Mantel-Haenszel method.In this case, multiple comparisons are also computed so as to not assume sphericity. The Greenhouse-Geisser correction allows repeated measures one-way ANOVA to work, even when the assumption of sphericity is violated because the repeated measurements are made in too short a time interval, so that random factors that cause a particular value to be high (or low) don't wash away or dissipate before the next measurement. ![]() Prism 6 now allows up to 256 subcolumns, so can perform repeated measures two-way ANVOA with up to 256 subjects per treatment. ![]() ![]() Prism 6 can handle repeated measures in both factors. Prism 5 could only compute two-way ANOVA with repeated measures in one of the factors. Two-way ANOVA with repeated measures in both factors. ![]()
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