Question

A random sample of 64 freshmen spent an average of 14 hours per week watching television. the sample standard deviation was 32 hours per week. what is the critical value for a 95% confidence interval for the population mean?

Answer 1

+/- 1.9983

Explanation:

The critical values for a confidence interval for the population mean, with population standard deviation not known, are obtained from the student's t distribution.

The sample size is given as 64. The degrees of freedom will thus be;

sample size - 1 = 64 - 1 = 63

The confidence level is given as 95%. The level of significance will thus be;

100 - 95 = 5%.

The area in the right-tail will thus be 2.5%. Therefore, we looking for a t-value such that the area to its right is 2.5% and the degrees of freedom being 63. From the t-tables we have;

+/- 1.9983