Posted by **Sue** on Sunday, May 26, 2013 at 10:05am.

The accompanying data show the number of hours, x, studied for an exam and the grade received, y (y is measured in tens; that is, y = 8 means that the grade, rounded to the nearest 10 points, is 80).

x 2 3 3 4 5 5 5 6 6 6 7 7 7 7 8

y 5 5 6 5 6 7 8 6 9 8 7 9 10 8 9

Maple Generated Plot

(a) Use the given scatter diagram to estimate r for the sample data on the number of hours studied and the exam grade.

r ¡Ö

(b) Calculate r. (Give your answer correct to two decimal places.)

r =

- Statistics -
**MathMate**, Sunday, May 26, 2013 at 10:07am
Are you expected to use Maple to do this exercise?

What are the answers?

- Statistics -
**Sue**, Sunday, May 26, 2013 at 10:12am
There is a diagram but I wasn't sure what to call it so I did not know how to look it up. I cant find anything in this chapter on how to calculate r? Or Maple.

- Statistics -
**MathMate**, Sunday, May 26, 2013 at 10:30am
Maple can certainly find r, called the coefficient of correlation.

The coefficient of correlation, r, for a population can be calculated using the following formula (one of the different forms):

r=(nΣxy-(Σx)( Σy)) / √[(nΣx²-(Σx)²)(nΣy²-(Σy)²)]

where

n=number of observations in the population.

The formula looks scary, but if you form a table and calculate the summations systematically, it would not take more than a few minutes.

For a check, r approximately equals 0.8.

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