21. Bigger portfolio. The class in Exercise 19 expands its stock-picking experiment.

a) The students use computer-generated random numbers to choose 25 stocks each. Use the 68–95–99.7 Rule to describe the sampling distribution model.

b) Confirm that you can use a Normal model here.

c) They increase the number of stocks picked to 64 each.

Draw and label the appropriate sampling distribution model. Check the appropriate conditions to justify your model.

d) Explain how the sampling distribution model changes as the number of stocks picked increases.