25. A school board commissions a study of the absentee rate of students at a particular high school in Vancouver For a random sample of 20 student records from the previous year, the mumber of days absent in the previous year is recorded, yielding = 40 and s = 4.

a) Stating the necessary assumptions, calculate a 95% confidence interval for the incan number of days absent for all students at that high school during the previous year.

b) Does the normality assumption scem plausible for these data? Explain, and discuss the implications of the ten "robustness" for your analysis.