posted by Lindsey on .
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?
None of the above
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.