Eight students in a particular college course are given a pre-test at the beginning of the semester and are then given the same exam at the end to test what they have learned. The exam scores at the beginning and at the end are given in the following table.

Let ????d be the mean difference End − Beginning. Compute a point estimate for ????d.

Student 1 2 3 4 5 6 7 8 End 83 71 79 95 84 72 69 78 Beginning 72 58 76 81 69 63 71 77