The Iowa Department of Public Education plans to select a simple random sample of teachers to estimate the aver-age days of sick leave taken last year by public school teachers in the state. Coordinators of the study initially decide to construct a confidence interval that is no wider than ± .5 days. Making a rough estimate of the variability in the population, the required sample size is determined. For each of the cases below, indicate whether the appropriate sample size would increase, decrease, or stay the same. (If the direction of the change cannot be deter-mined without more specific information, so indicate.) Assume any factor not mentioned remains constant.

a. You want a higher level of confidence.

b. You want a tighter interval.

c. The variation of values in the population is less than you had initially estimated.

d. You decide that you can live with a lower confidence level. There is more variability in the population of values than you had first estimated.

e. You want a tighter interval. You require a higher level of confidence. There is less variability in the population of values than you had first estimated.