The article “Dynamics of Insulin Action in Hypertension: Assessment from Minimal Model Interpretation of Intravenous Glucose Tolerance Test Data” (R. Burattini, M. Morettini, et al., Med Biol Eng Comput, 2011:831–841) compared levels of an insulin sensitivity index S_I in patients with high blood pressure and patients with normal blood pressure. Ten patients with high blood pressure had a mean value of 3.4 with a standard deviation of 0.6, and eight patients with normal blood pressure had a mean value of 7.9 with a standard deviation of 0.6. Units are 10⁻⁵· min⁻¹· pmol⁻¹. Find a 98% confidence interval for the difference in mean levels between those with high blood pressure and those with normal blood pressure.