Question

A survey is given to students to study the cost of textbooks this semester. A random sample of 12 students had an average cost of $284.90 and a standard deviation of $96.10. Find a 95% confidence interval for the average textbook cost for all students assuming the cost of textbooks are normal.

Answer 1

Solution :

t _/2,df = 2.201

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

= 2.201 * (96.10 / 12)

Margin of error = E = 61.06

The 95% confidence interval estimate of the population mean is,

- E < < + E

284.90 - 61.06 < < 284.90 + 61.06

223.84 < < 315.96

(223.84 , 315.96)