Question

The graph below plots the values of y for different values of x:

Plot the ordered pairs 1, 8 and 2, 3 and 3, 0 and 4, 1 and 5, 2 and 6, 1

What is the correlation coefficient for the data plotted?

−0.9
−0.6
0.6
0.9

Answer 1

X Values

∑ = 21

Mean = 3.5

∑(X - Mx)2 = SSx = 17.5

Y Values

∑ = 15

Mean = 2.5

∑(Y - My)2 = SSy = 41.5

X and Y Combined

N = 6

∑(X - Mx)(Y - My) = -18.5

R Calculation

r = ∑((X - My)(Y - Mx)) / √((SSx)(SSy))

r = -18.5 / √((17.5)(41.5)) = -0.6865

Meta Numerics (cross-check)

r = -0.6865

Answer 2

-0.6

Explanation:

we know that

The correlation coefficient is a measure of the strength of the straight-line or linear relationship between two variables. Correlation coefficients are expressed as values between +1 and -1

we have

(1,8),(2,3),(3,0),(4,1),(5,2),(6,1)

using a Excel tool (CORREL function)

see the attached table

The correlation coefficient is -0.68