Actual and Forecast Temperatures Data Set 10 in Appendix B includes a list of actual high temperatures and the corresponding list of three-day forecast high temperatures.

If the difference for each day is found by subtracting the three-day forecast high temperature from the actual high temperature, the result is a list of 31 values with a mean of 20.419° and a standard deviation of 3.704°. Use a 0.05 significance level to test the claim that the mean difference is different from 0°. Based on the result, does it appear that the three-day forecast high temperatures are reasonably accurate?