It is hypothesized that the environment in which students appear for a test might impact their scores. An experiment was designed to test the effects of music and temperature in the classroom in which a midterm test was being conducted. Twenty students with similar scores in a previous midterm test in the same subject were randomly selected out of 40 students. They were then randomly divided into four groups. Group A had music in the room and a temperature of 22 degrees Celsius during the midterm test. Group B had no music and 22 degrees Celsius. Group C had music and 25 degrees Celsius. Group D had no music and 25 degrees Celsius. The file Midterm contains the scores of the students on the basis of their group (the maximum score was 50).

a. At the 0.05 level of significance, is there evidence of a difference in the mean midterm scores of the different groups?

b. If appropriate, determine which group differs in mean midterm scores.

c. At the 0.05 level of significance, is there evidence of a difference in the variation in the mean midterm scores of the different groups?