statistics
posted by Cam .
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.
1. Identify the population mean.
2. Identify the population standard deviation.
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 100 people over 55 is selected. What is the probability that the sample mean will be below 7?

With your data, these are the best estimates.
1. 8
2. 2
3. Z = (scoremean)/SEm
SEm = SD/√n
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability relate to the Z score.
4. Same process as 3.