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Statistics

Notes Table for Calculation of r

Substituting various values in the formula for r, we get
40   44  6 12   1832
r     0.903
40 50 36 40 56 144 1964 2096




Examples 14:
Given the following data, compute the coefficient of correlation r, between X and Y.

Y 
30-50 50-70 70-90 Total
X 
0-5 10 6 2 18
5-10 3 5 4 12
10-15 4 7 9 20
Total 17 18 15 50

Solution.
Note: Instead of doing the computation work in a single table, as done in example 13, it can be
split into the following steps:
Taking mid-values of the class intervals, we have
Mid-values (X) : 2.5 7.5 12.5

Mid-values (Y) : 40 60 80
X  7.5 Y  60
Let u  i and v  i
i i
5 20
 various u values are : - 1 0 1
and various v values are : - 1 0 1

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