This question was answered using a Z test. i am resending ( correct me if I'm wrong). the sample size is 20 and i believe should call for T test. since it is less than 30.

A local university requires that all first year students complete a math course during first semester. This year the university is evaluating a new online version of the course. A random sample of n = 20 students is selected and the students are placed in the online course. At the end of the semester, all students take the same math exam. The average score for the sample of n = 20 students is M = 85. For the general population of students who took the traditional lecture class, scores on the exam are normally distributed with a = 75 and = 15.

Can we conclude that scores on the math exam for the sample of students who took the new online course are significantly different from those of the general population of students (who took the traditional lecture course)? Use a two-tailed test with = .05. Be sure to state your null hypothesis, a decision about that null hypothesis, and a conclusion explaining your results with an format statement. Calculate Cohen's d if necessary.