It is known that the weight of cats has standard deviation 3 pounds. We want to estimate the mean weight
of the entire population of cats using a sample of 40 randomly selected cats.
(a) Find the standard deviation of the sample mean.
(b) Find the probability that the sampling error is less than 1 pound.
(c) Suppose that, for our sample, the mean weight is 11 pounds. How con?dent can we be that the population mean is between 10 and 12 pounds?