2 Suppose you collected data on the distance between the two

2. Suppose you collected data on the distance between the two eyes of insects
(eyespan) from two different and independent groups of individuals raised on corn and
cotton diets (see frequency distributions below). Yes, people do look at this stuff. Males with longer eyespans are apparently more attractive to
females, and so researchers have tested whether environmental conditions during growth,
particularly the diet, affects their adult eyespan. So the distributions below are based on
the eyespans for each individual. Suppose you want to test the difference between the
means of the two groups. Of the tests listed below, what is the most appropriate test to
use with these data and why?

Your choices
a) t-test because the variances are the same and

there are over 30 individuals in each group

b) Welch’s t-test because the variances look

different

c) Mann-Whitney U test because there are

severe outliers in both groups

d)Wilcoxon signed-rank test because the data are pair of eyespans, and thus the data have to be paired, rather than independent

Solution

a) t-test because the variances are the same and

there are over 30 individuals in each group