An editor wants to estimate average the number of pages in bestselling novels, so that his estimate falls within 20 sheets of the true average. Assuming that the standard deviation is 69 sheets, how large a sample of bestselling novels is needed to achieve

a. 90% confidence? (Your answer should be a whole number)

b. 95% confidence? (Your answer should be a whole number)

c. Identify the variable in this context

d. Identify an individual in this context