Fruit flies, like almost all other living organisms, have built-in circadian rhythms that keep time even in the absence of external stimuli. Several genes have been shown to be involved in internal timekeeping, including per (period) and tim (timeless). Mutations in these two genes, and in other genes, disrupt timekeeping abilities. Interestingly, these genes have also been shown to be involved in other time-related behavior, such as the frequency of wingbeats in male courtship behaviors. Individuals that carry particular mutations of per and tim have been shown to copulate for longer than individuals that have neither mutation. But do these two mutations affect copulation time in similar ways? The following table summarizes some data on the duration of copulation for flies that carry either the tim mutation or the per mutation (Beaver and Giebultowicz 2004).

Mutation Mean copulation duration (min) Standard deviation of copulation duration Sample size, n
per 17.5 3.37 14
tim 19.9 2.47 17

Assume that the copulation time data are normally distributed. Do tim and per mutations lead to different mean copulation durations? Determine the absolute value of the test statistic for the appropriate test.