ABSTRACT
An essential data analysis compares the values of a continuous variable across two or more groups to detect possible population differences in the variable across samples from the respective groups. One comparison is of the means of the two groups, the estimation of the mean difference. Or, if the group consists of matching pairs of data, then compare the differences directly. Need to analysis are the t-test for independent groups and the t-test for dependent groups, respectively. Accomplish both analyses with the lessR function t_test(). The corresponding nonparametric tests are also discussed. Comparisons are made both for groups based on observational data and experimental data. The special case of the mean, the proportion, is also compared across groups.
