Now say that you multiply x by 3 and multiply y by 3 and ree

Now say that you multiply x by 3 and multiply y by 3 and re-estimate the model. What will be your new estimate of the slope parameter?

Solution

When we multiply x by 3 and y by 3, x bar and y bar become 3x bar and 3y bar

New var = 9 old variance

Hence new std dev = 3 (2.2195)

r will be the same
Slope = sy/sx (r) = 3sy/3sx(r)

Hence slope remains the same.