Question

150 subjects in a psychological study had a mean score of 36 on a test instrument designed to measure anger. The standard deviation of the 150 scores was 12. Find a 98% confidence interval for the mean anger score of the populations from which the sample was selected.

Select one: a. (34.1, 37.9) b. (33.5, 38.5) c. (33.7, 38.3) d. None of other answer is necessary true.

Answer 1

Solution :

Given that,

t /2,df = 2.352

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

= 2.352 * (12 / 150)

Margin of error = E = 2.3

The 98% confidence interval estimate of the population mean is,

- E < < + E

36 - 2.3 < < 36 + 2.3

33.7 < < 38.3

(33.7 , 38.3)

option c. is correct