Transcript Lecture 12 Slides (example)

Monday, November 5
The familiar t distribution, at N-2 degrees of
freedom, can be used to test the probability that the
statistic r was drawn from a population with  = 0
H0 :  XY = 0
H1 :  XY  0
where
r
N-2
t=
1 - r2
Question
• If you were to predict the height of your
first child when he or she is an adult,
which of the following two pieces of
information would you rather know:
(1) Whether the child is a boy or a girl; or
(2) The height of the same-sex biological
parent.
Pearson’s r
-1  r  +1
-1    +1
Pearson’s r can also be interpreted as the expected value of zY given a value of zX.
tend to deviate from the mean of X when they are expressed in standard deviation units.
The expected value of zY is zX*r
If you are predicting zY from zX where there is a perfect correlation (r=1.0), then
zY=zX.. If the correlation is r=.5, then zY=.5zX.