Question

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?

Answer 1

With your data, these are the best estimates.

1. 8

2. 2

3. Z = (score-mean)/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.