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Comparing two groups 

Comparing two groups
Comparing two groups
Presenting Medical Statistics from Proposal to Publication (2 ed.)

Janet L. Peacock

, Sally M. Kerry

, and Raymond R. Balise


Chapter 7 discusses comparing two groups, and covers graphical presentation of continuous unpaired data, the two-sample t test, and the Mann-Whitney U test. It describes the use of data transformations and how results are interpreted. It shows how to compare two proportions using the chi-squared test and how to report results as differences in proportions, relative risks, and odds ratios. It includes how to calculate 95% confidence intervals for estimates. Finally, the chapter discusses the reasons for and consequences of dichotomization of continuous data and a method for dichotomization without losing statistical power. The chapter includes analyses using Stata, SAS, SPSS, and R.

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