Question 9

Suppose our Registration and Examinations Section (RES) want to study absenteeism among Year 4 students of Faculty of Social Sciences during the year. A random sample of 25 Year 4 students reveals the following:

Absenteeism: X =9.7 days, s=4.0 days

a) Set up a 95% confidence interval estimate of the average number of absences for year 4 students. Give a practical interpretation of the interval obtained.

b) What assumption must hold in order to perform the estimation in (a)?

c) If RES wants to take a survey again, what sample size is needed if they want to be 95% confident of being correct to within 1.5 days and the population standard deviation is

assumed to be 4.5 days?