“I have 5 groups of 10 cases in my data. How can I draw a stratified random sample from these cases? That is, from groups 1 through 5 I’d like to draw exactly 5, 4, 5, 6 and 3 cases at random. What’s an efficient way to do this?” Before and after drawing our stratified […]
Sampling is at the very core of statistical tests: drawing conclusions on research populations based on (small) samples from those populations. Basically all statistical tests quietly assume that the data you’re analyzing are a simple random sample from your population. This assumption being ignored is the very reason why political polls are often widely off and research findings can’t be […]
DO REPEAT is a command for running other commands repetitively.SPSS DO REPEAT is often used for looping over (possibly new) variables. VECTOR with LOOP is an alternative way for doing so. Introduction Suppose we have a variable containing values 1 through 4 and we’d like to dichotomize it for a regression analysis. (For some more background, see Creating Dummy Variables in SPSS.) […]
Introduction Popular statistical procedures such as ANOVA, a chi-square test or a t-test quietly rely on the assumption that your data are a simple random sample from your population. Violation of this assumption may result in biased or even nonsensical test results and few researchers seem to be aware of this. Plenty of reasons for a brief discussion of simple […]
