CH 4B
SCATTERPLOT And CORRELATION
Example 1
I wish to determine the correlation between the height (in inches) and weight (in pounds) of 21
‑
year
‑
old
males. To do this, I measure the height and weight of two 21
‑
year
‑
old men. The measured values are:
Male #1
Male #2
Height
70
69
Weight
160
164
The correlation
𝑟
computed from the measurements on these males is:
a. 1.0.
b. near 0, because the heights and weights of the men are similar.
c. -1.0.
Example 2
A statistics student computes the correlation between two variables in her spreadsheet and finds
𝑟
=0.06.
She concludes there is no relationship between the variables. Is she correct?
a. yes
b. We do not have enough information to answer the question.
c. no
Example 3
A recent article in an educational research journal reports a correlation of
+0.8
between math
achievement and overall math aptitude. It also reports a correlation of
−0.8
between math
achievement and math anxiety.
Which of the following interpretations is the most correct?
a. The correlation of
+0.8
is just as strong as the correlation of
−0.8.
b. It is impossible to tell which correlation is stronger.
c. The correlation of
+0.8
indicates a stronger relationship than the correlation of
−0.8.