You would like to construct a

99%

confidence interval to estimate the population mean PCB (Polychlorinated biphenyl) level in white croaker fish from the San Francisco Bay. The random sample we select has a mean of

637

parts per million and a standard deviation of

55

parts per million.

(a) What is the best point estimate, based on the sample, to use for the population mean? 637partspermillion

(b) For each of the following sampling scenarios, determine which distribution should be used to calculate the critical value for the

99%

confidence interval for the population mean.

(In the table, Z refers to a standard normal distribution, and