Question

40 final exams scores are selected from all students enrolled in French II. Of those 40, their mean is found to be 82.3 and their standard deviation is found to be 7.2. Construct a 90% confidence interval for the mean of all students enrolled in the class.

Answer 1

Solution :

Given that,

t /2,df = 1.685

Margin of error = E = t/2,df * (s /n)

= 1.685 * (7.2 / 40)

Margin of error = E = 1.9

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

- E < < + E

82.3 - 1.9 < < 82.3 + 1.9

80.4 < < 84.2

(80.4 , 84.2)