The average weekly earnings of all bus drivers in a city are $950 (this is ) with a standard deviation of $45 (this is ). Assume that we select a random sample of 81 bus drivers.

What is the probability distribution of the sample mean? Explain.

Assume the number of bus drivers in the city is large compared to the sample size. Compute

the standard error of the mean.

What is the probability that the sample mean will be greater than $960?

If the population of bus drivers consisted of 400 drivers, what would be the standard error of

the mean?