A specific study found that the average number of doctor visits per year for people over 55 is 8 with a standard deviation of 2. Assume that the variable is normally distributed.

3. Suppose a random sample of 15 people over 55 is selected. What is the probability that the sample mean is above 9? 4. Suppose a random sample of 10 people over 55 is selected. What is the probability that the sample mean will be below 7?

7. Find the probability that a sample of 20 citizens will have a mean less than $1800. 8. Find the probability that a sample of 50 citizens will have a mean less than $2000.