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.

The population mean is 8.
2. Identify the population standard deviation.

The population standard deviation is 2.
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?

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  1. 1 & 2 are right.

    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 related to the Z score.

    4. Use same process.

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