Many statistical tests have assumptions that must be true for the test results to be
valid. A pooled sample t-test assumes that the samples are normally distributed and the
variances of the groups are equal. It can be useful to verify the assumptions.
A Shapiro-Wilk normality test is added to the analysis task
A Levene test for variances is added to the analysis task
The p-value of the normality test is not significant so do not reject the null
hypothesis. The data can be treated as normally distributed.
(click to enlarge)
The p-value of the
homogeneity of variance test is 0.04 so reject the null hypothesis of homogeneity of
variances in favor of the alternative hypothesis of a difference in variances.