Other's On-Line Resources (Chapter 9)
| Estimation
With r |
- Description:
This interactive on-line resource allows you to build a 95% confidence
interval around a correlation coefficient, with you being able
to specify both r and n.
- What to Do:
- Click on the colored title of this on-line resource: "Estimation
With r."
- Enter, in the "r" box, any number you want for the sample
correlation coefficient.
- Enter, in the "n" box, any number you want for the sample
size.
- Click on the gray bar that says "Calculate the Confidence
Interval."
- On the next screen that pops up, look at the CI that's been
built for your situation.
- Click on your browser's "Back" button, and then repeat Steps
2-5, varying the values of r and n.
- Sky Huck's Puzzle Question:
There are 2 ways to get the CI to extend above r PRECISELY
the same extent as it extends below r. Can you demonstrate
BOTH of them using this on-line resource?
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| Is
r Significant? |
- Description:
You'll see several correlation coefficients generated from a real
study. In this investigation, people were measured in terms of
two variables (isometric strength and job performance), with two
different measures taken on each of these variable. The bivariate
correlation coefficients are presented in a correlation matrix,
with each r tested to see if it was statistically significant.
- Sky Huck's Question to you:
What kind of relationship exists between the values of r and p
in the correlation matrix? Is it a direct relationship or an indirect
relationship?
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| Comparing
2 Correlations |
- Description:
This interactive resource allows you to see if there is a statistically
significant difference between two correlation coefficients. By
exerting control over (1) the size of the difference between the
two rs and (2) the sample sizes, you'll be able to see that large
sample sizes can turn a small difference into something "significant."
- What to Do:
- Click on the colored title of this on-line resource: "Comparing
2 Correlations."
- Make 2 private decisions: (a) your level of significance
and (b) whether you want to do a one-tailed test or a two-tailed
test.
- Enter .50 and .55 as the r values for Samples A and B.
- Enter 100 for each sample size.
- Click "Calculate" and then look to see if you have a statistically
significant finding; this will be the case if the computed
p is smaller that the alpha level you selected in Step #2.
- If you don't have a significant finding, repeat Steps #4
and #5 again and again (each time increasing each n by 100)
until you finally can cross over into "The Wonderful Land
of Significance."
- Sky Huck's Puzzle Question:
What do you think will happen to the computed value of p if you
(1) set each n equal to 100, (2) make the two values of r different
by .20, and (3) change the "location" of your two r values on
the "correlation continuum" (that extends from -1.00 to +1.00)?
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