Microsoft Office Tutorials and References
In Depth Information
Fig. 6.8 Worksheet for Computing the Correlation, r
Notice that when Excel multiplies a minus number by a minus number, the result
is a plus number (for example for student #7: (
0.29.
And when Excel multiplies a minus number by a plus number, the result is a
negative number (for example for student #1: (
0.46) x (
0.64)
¼þ
0.06) x (
þ
0.16)
¼
0.01 .
Note: Excel computes all computation to 16 decimal places. So, when you check
your work with a calculator, you frequently get a slightly different answer than
Excel’s answer.
For example, when you compute above:
X
Y
ð
X
Þ
x
ð
Y
Þ
for student #2
your calculator gives :
(6.2)
;
(
0.0216
As you can see from the table, Excel’s answer is
0.36) x (
þ
0.06)
¼
0.02 which is really more
accurate because Excel uses 16 decimal places for every number, even though only
two decimal places are shown in Figure 6.8 .
You should also note that when you do Step 6, you have to be careful to add all of
the positive numbers first to get
þ
1.10 and then add all of the negative numbers
1.07
as your answer to Step 6. When you do these computations using Excel, this total
figure will be
0.03 , so that when you subtract these two numbers you get
þ
second to get
1.09 because Excel carries every number and computation out to 16
decimal places which is much more accurate than your calculator.
þ
7. Multiply the answer for step 2 above by the answer for step 6
(0.14286 x 1.09)
0.1557
8. Multiply the STDEV of X times the STDEV of Y (0.48 x 0.39)
0.1872
9. Finally, divide the answer from step 7 by the answer from
step 8 (0.1557 divided by 0.1872)
þ
0.83
This number of 0.83 is the correlation between HSGPA (X) and FRGPA (Y) for
these 8 students. The number
þ
0.83 means that
there is a strong, positive
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