Rework Exercise 14.71, coding the class marks of the history scores €“2, €“1, 0, 1, and 2 and the class marks of the economics scores €“2, €“1, 0, 1, 2, and 3. (It follows from Exercise 14.70 that this kind of coding will not affect the value of r.)

In exercise
The table at the bottom of the page shows how the history and economics scores of 25 students are distributed. Use the method of Exercise 14.32 to determine the value of r, replacing the row headings by the corresponding class marks (midpoints) 23, 28, 33, 38, 43, and 48 and the column headings by the corresponding class marks 23, 28, 33, 38, and 43. Use this value of r to test at the 0.05 level of significance whether there is a relation-ship between scores in the two subjects.

History scores 21-25 26-30 31-35 36-40 41-45 21-21 26-30 31-35 36-40 41-45 46-50