7. Suppose that in a certain region of the country the mean duration of first marriages that end in divorce is 7.8 years with a standard deviation of 1.2 years. Find the probability that in a sample...

Extracted text: 7. Suppose that in a certain region of the country the mean duration of first marriages that end in divorce is 7.8 years with a standard deviation of 1.2 years. Find the probability that in a sample of 75 divorces, the mean age of the marriages is at most 8 years.