Question

A teacher wants to compare the mean geology scores of two different classes. She is testing the null hypothesis that there is no difference in the population mean scores of the two classes. The difference of the sample means is 51.4. If the standard deviation of the distribution of the difference of sample means is 16.66, what is the 95% confidence interval for the population mean difference? A)between -33.2 and + 33.2 B)between -49.9 and +49.9 C)between -102.8 and +102.8 D)between -154.2 and +154.2

Answer 1

The 95% confidence interval is equal to two standard deviations either side of the mean, so in this case, the answer would be +/-(2 * 16.6) from the mean, or -33.2 and +33.2 points from the sample mean. This would give a response of A.