For a data set with D: 0, 5, 10, 15, 20, 25, 30, 35 and corresponding M: 90, 82, 56, 68, 58, 46, 30, 20, what is the product moment correlation coefficient r, to 3 decimal places?

Model answer

-0.957

Also accepted: -0.96, -0.958

Explanation

Using Sxy = -1975, Sxx = 1050 and Syy = 4051.5, r = Sxy / sqrt(Sxx x Syy) = -1975 / sqrt(4254075), which is approximately -0.957.

Derived from ZIMSEC Statistics Paper 2, November 2018, Q7

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