As the principal of a private high school, you are interested in finding out how the training in mathematics at your school compares with that of the public schools in your area. For the last 5 years, the public schools have given all graduating seniors a mathematics proficiency test. The distribution has a mean of 80. You give all the graduating seniors in your school the same mathematics proficiency test. The results show a distribution of 28 scores, with a mean of 85 and a standard deviation of 12.2.

I keep getting the wrong T critical value for some reason please help!! thanks!