In a study done for Milestone magazine a random sample of su

In a study done for Milestone magazine, a random sample of subscribers was selected. Each subscriber in the sample was asked to recall advertisements in this month\'s edition of the magazine. Assume all of the necessary conditions are met regarding the data. The average number of advertisements recalled was 8.2 with a sample standard deviation of 3.6. Calculate the 95% Confidence Interval assuming they randomly interviewed 21 subscribers

Solution

Given that n = 21 mean = 8.2 Standard deviation = 3.6

The 95% confidence limits is given by    X ± t_0.05 S/n

The table value for t_0.05 for (21-1) i.e., 20 degrees of freedom is 2.086

X ± 2.086 (S/n)

8.2 ± 2.086 (3.6/21)

[6.5613 , 9.8387]