2. The substance 3,4-dihydroxyphenylacetic acid (DOPAC, ng/ml) is a neuroactive metabolite in the tryptophan (TRP) pathway. A study was conducted to explore the differences in the concentration of DOPAC in the serum between male and female mice; the corresponding results are summarized in Table 6.4 (assuming the concentration of DOPAC is normally distributed and the population variances of male and female mice are equal).

(a) Provide interval estimates of the mean and variance of the concentration of DOPAC of male mice.

(b) Which method would you use to construct the CI of the mean difference in the concentration of DOPAC in TRP pathways in the serum between male and female mice: Z or t ? Justify your choice and estimate the mean difference.

(c) Estimate the ratio of variances between male and female mice.