To help consumers assess the risks they are taking, the Food and Drug Administration (FDA) publishes the amount of nicotine found in all commercial brands of cigarettes. A new cigarette has recently been marketed. The FDA tests on this cigarette yielded mean nicotine content of 28.8 milligrams and standard deviation of 2.1 milligrams for a sample of cigarettes. Construct a 90% confidence interval for the mean nicotine content of this brand of cigarette.

a. The population of total compensations of CEOs in the service industry is approximately normally distributed.
b. The distribution of the sample means is approximately normal.
c. The sample standard deviation is less than the degrees of freedom.
d. None. The Central Limit Theorem applies.