The Professor's Response
Hi Professor Im struggling with a questions that seems pretty simple!
Ch. 10 #3 in the homework. Im doing everything right except for the SST, I'm adding 1368squared/4 + 1279squared/4 + 1471squared/4 + 1454squared/4 = 1946305.5
Then i go on to do the SSE and I subtract 31121.333-1946305 and get -1915183.667
I don't know what I'm doing wrong
See the professor's answer below.
Hi Sandra,
You haven't subtracted your correction factor from the 1,946,305.5. Don't forget the correction factor is (Σy)² /N.
Hope that helps,
Professor McGuckian
The prediction error is y - ^y . The variable y represents the actual y value from the original data that corresponds to the x value they are using. The ^y value is the value the regression equation you created gives you when you plug the x into the equation.
Hi Sandra,
If you understood part a, then part b is easy. Part a gives us the variance, s², so we just take the square root of the answer in part a and then multiply by two. The reason we multiply by two is that we assume the error terms have a normal distribution with a mean of zero. The empirical rule from STATS I tells us that approximately 2 standard deviations capture 95% of the data under a bell curve.
Professor McGuckian