Posted by **Lindsey** on Monday, February 18, 2013 at 5:04pm.

Suppose a data set has a linear regression line of y = 6 -0.8x. If the mean of the x's is 5, what is the mean of the y's?

2

5

10

6

None of the above

- Statistics -
**MathGuru**, Monday, February 18, 2013 at 8:38pm
The mean of the y's = 2

Use this equation:

predicted y = (rSy/Sx)X - (rSy/Sx)xbar + ybar

...where r = correlation, Sy = sd of y, Sx = sd of x, and X is the variable in 'a + bx' equation.

Note: xbar = mean of x; ybar = mean of y.

Substituting what is known:

predicted y = (-0.8)X - (-0.8)5 + ybar

predicted y = (-0.8)X - (-4) + ybar

predicted y = (-0.8)X + 4 + ybar

predicted y = (-0.8)X + 4 + 2

predicted y = (-0.8)X + 6

Therefore: ybar = 2

I hope this helps.

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