The t Test Procedure 149
A t TEST is a procedure used for comparing sample means to see if there is sufficient evidence to infer that the means of the corresponding population distributions also differ. More specifically, for an independent-samples t test, a sample is taken from two populations. The two samples are measured on some variable of interest. A t test will determine if the means of the two sample distributions differ significantly from each other. t tests may be used to explore issues such as: Does treatment A yield a higher rate of recovery than treatment B? Does one advertising technique produce higher sales than another technique? Do men or women score higher on a measure of empathic tendency? Does one training method produce faster times on the track than another training method? The key word is two: t tests always compare two different means or values.