10.68 A study was conducted to assess the safety and efficiency of receiving nitroglycerin from a transdermal system (i.e., a patch worn on the skin), which intermittently delivers the medication, versus taking oral medication (pills). Twenty patients who suffer from angina (chest pain) due to physical effort were enrolled in trials. All received patches, some (n  8) contained nitroglycerin;

the others (n  12) contained a placebo. Suppose the resulting “time to angina” data were summarized:

Mean Time to Angina (sec)

Active Placebo Difference SE p-Valuea Day 1 AM 320.00 287.00 33.00 9.68 0.0029 Day 7 PM 314.00 285.25 28.75 13.74 0.0500 aFor treatment difference.

a. Determine the value of t for the difference between two independent means given the difference and the standard error (SE) for the day 1 AM data. Assume normality.

b. Verify the p-value.

c. Determine the value of t for the difference between two independent means given the difference and the standard error (SE) for the day 7 PM data.

d. Verify the p-value.