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# Continuous Outcomes

 Groups Purpose Conditions or Assumptions Test Descriptive Measures (also used to calculate CIs) Single sample Compare mean to historical or hypothetical (known) mean Standard deviation known or N large and approximate normality One-sample z-test Mean, std deviation, difference from historical mean Compare mean to historical or hypothetical (known) mean Standard deviation unknown; approximate normality One-sample t-test Mean, std deviation, difference from historical mean Two independent samples Compare means Approximate normality Two-sample t-test Means, std deviations, pooled std deviation, difference in means Compare medians (Pr (X < Y)) Use for highly non-normal outcomes Wilcoxon rank-sum test Mann-Whitney U test Medians, quartiles, difference between medians Two+ independent samples Compare means (any or overall difference) Approximate normality Analysis of variance (ANOVA) Means, std deviations, pairwise differences in means Compare medians (outcome distributions) Use for highly non-normal outcomes Kruskal-Wallis test Medians, quartiles, pairwise differences in medians Matched Pairs (2) Evaluate whether mean of differences nonzero Approximate normality Paired t-test Mean of differences, std deviation of differences Evaluate whether median of differences nonzero Use for highly non-normal outcomes Wilcoxon sign-rank test Median of differences, quartiles of differences Evaluate whether mean of differences nonzero Approximate normality Repeated measures ANOVA Mean of differences, std deviation of differences Evaluate whether median of differences nonzero Use for highly non-normal outcomes Friedman test Median of differences, quartiles of differences

rev. 29-Aug-2016