An article in IEEE International Symposium on Electromagnetic Compatibility (2002, Vol. 2, pp. 667–670) quantified the absorption of electromagnetic energy and the resulting thermal effect from cellular phones. The experimental results were obtained from in vivo experiments conducted on rats. The arterial blood pressure values (mmHg) for the control group (8 rats) during the experiment are x̅₁ = 90, s₁ = 5 and for the test group (9 rats) are x̅₂ = 115, s₂ = 10.

(a) Is there evidence to support the claim that the test group has higher mean blood pressure? Use α = 0.05, and assume that both populations are normally distributed but the variances are not equal. What is the P-value for this test?

(b) Calculate a confidence interval to answer the question in part (a).

(c) Do the data support the claim that the mean blood pressure from the test group is at least 15 mmHg higher than the control group? Make the same assumptions as in these part (a).

(d) Explain how the question in part (c) could be answered with a confidence interval.