Question

A random sample of 28 statistics tutorials was selected from the past 5 years and the percentage of students absent from each one recorded. The results are given below. Assume the percentages of students' absences are approximately normally distributed. Use Excel to estimate the mean percentage of absences per tutorial over the past 5 years with 90% confidence. Round your answers to two decimal places and use increasing order. Number of Absences 13.9 16.4 12.3 13.2 8.4 4.4 10.3 8.8 4.8 10.9 15.9 9.7 4.5 11.5 5.7 10.8 9.7 8.2 10.3 12.2 10.6 16.2 15.2 1.7 11.7 11.9 10.0 12.4

Answer 1

Solution:

The calculation for the sample mean and sample standard deviation by use of Excel is given below.

	Number of Absent in ascending order
	1.7
	4.4
	4.5
	4.8
	5.7
	8.2
	8.4
	8.8
	9.7
	9.7
	10
	10.3
	10.3
	10.6
	10.8
	10.9
	11.5
	11.7
	11.9
	12.2
	12.3
	12.4
	13.2
	13.9
	15.2
	15.9
	16.2
	16.4
Average	10.41428571
Variance	13.7768254