In experiments to determine the effectiveness of drugs

Chapter 5, Problem 7E

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In experiments to determine the effectiveness of drugs such as antifungal ointments that are applied to the skin, the concentration of the drug in a patient’s skin  must be measured. The article “Determining Bio- equivalence of Topical Dermatological Drug Products  by Tape-Stripping” (W. Navidi, A. Hutchinson, et al.,  Journal of Pharmacokinetics and Pharmacodynam- ics, 2008:213–220) describes an improved method of  measuring that is designed to ensure that all the drug  in the skin is recovered. Assume that in an experi- ment using the old method, the mean amount of drug  recovered from a sample of 49 patients was 105 ng  with a standard deviation of 20 ng, and that in an experiment using the new method the mean amount of  drug recovered in a sample of 35 patients was 117 ng  with a standard deviation of 15 ng. Find a 98% confidence interval for the difference in the mean amounts  recovered between the two methods.