Evaluate the expression 42 - d when d = 3.6 Ha

A marketing firm wishes to test the effectiveness of the audio/visual presentation of certain information as opposed to the purely audio presentation of the information.  To this end 100 volunteers were given a 10 minute presentation in which the information was presented in an audio/visual format.  A second group of 100 volunteers was presented the same information in a purely audio format.  Each person in each of the two groups was asked the same 20 questions related to the information in the presentation.   The audio/visual group had an average of 10.5 correct responses with a sample standard deviation of 4.  The purely audio group had an average of 9.4 correct responses with a standard deviation of 3.  The marketing firm believes this means that the audio/visual format leads to better retention of the information. We test the hypotheses H0:  1 -2=0 versus Ha: 1 -2>0 at a 2% level of significance.   Here  denotes  1 the population average number of correct responses for…

In a traditional class with in-class tests, a question that is often asked after a class exam is, "What was the class average?" If that question is asked and the professor says that the class average was 80, what information do the students gain by knowing that? I want you to focus on both what the individual students knows about their own grade as well as what the students know about the class's grades on that exam.

I need some explanation on these 3 problems.