Question

A random sample of 225 1st-year statistics tutorials was selected from the past 5 years and the number of students absents recorded. The results were a population mean of 11.6 with a standard deviation of 4.1 absences. Find the Confidence Interval of absences over the past 5 years with 90% confidence.

Answer 1

Solution :

Given that,

Sample size = n = 225

Z/2 = 1.645

Margin of error = E = Z/2* ( /n)

= 1.645 * (4.1 / 225)

Margin of error = E = 0.4

At 90% confidence interval estimate of the population mean is,

- E < < + E

11.6 - 0.4 < < 11.6 + 0.4

11.2 < < 12

(11.2 , 12)