posted by Sue on .
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.
(b) Calculate r. (Give your answer correct to two decimal places.)
Are you expected to use Maple to do this exercise?
What are the answers?
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.
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)]
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.