The FDA is testing a new ointment designed to deliver 3.5 micrograms of active ingredient to each square centimeter of skin. Nin
e(9) subjects apply the ointment and then six hours later that amount of drug absorbed by the skin is measured. To determine if there is enough evidence that the mean amount of drug absorbed is different from 3.5 micrograms at the α=0.01 significance level, we would need to compare our test statistic to what critical
We assume a normal distribution, and with sample size n = 9 we should follow a t -student test on both tails since the FDA is interested in determining if the amount of drug absorbed is different from 3.5 micrograms.
Therefore if α = 0,01 that means that confidence interval is 99 % or 0,99
Finally with α/2 = 0,005 and 8 degrees of freedom we find in t-student table t(c) = 3.355
