The labor relations manager of a large corporation wished to study the absenteeism among workers at the company's central office during the last year. a random sample of 25 workers revealed the following: an average of 9.7 days; a standard deviation of 4.0 days; and 12 employees were absent more than 10 days. In estimating the 95% confidence interval estimate of the proportion of workers absent more than 10 days last year would you use a z or t in the formula?