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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 -

    Are you expected to use Maple to do this exercise?
    What are the answers?

  • Statistics -

    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 -

    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.

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