Other's OnLine Resources (Chapter 8)
Statistical
Power 
 Description:
By using this interactive resource, you'll be able to (1) see
a wonderful picture that illustrates graphically the concept of
statistical power and (2) change one or more of four factors (e.g.,
sample size) snd then observe what happens to power as a consequence
of your change(s).
 What to Do:
 Click on the colored title of this online resource: "Statistical
Power."
 Scroll down to the bottom of the screen that pops up.
 Click on the "Show it" button below the large gray box.
 Enter this information in the various windows below the
gray box: True mean = 110, Hyp. mean = 100, sigma = 15, and
n = 25.
 Click again on the "Show it" button, and then look inside
the gray box at (a) the picture and (b) the power value presented
beneath the picture.
 Increase n to 50 and then click on "Show it" to see what
happens.
 Change other information in the input boxes and then click
on "Show it" to see what happens.
 Sky Huck's Puzzle Question:
The power value shown inside the large gray box is influenced
by 4 decisions you make concerning: (a) the difference between
the true and hypothesized means, (b) sigma, (c) n, and (d) whether
the test is onetailed or twotailed. Which of these 4 things
have a direct relationship with power, and which have an indirect
relationship?

Practical vs. Statistical Significance (A) 
 Description:
By using this interactive online resource, you'll be able to
see how statistically significant results can come about even
though the null hypothesis is just slightly false.
 What to Do:
 Click on the colored title of this online resource: "Practical
vs. Statistical Significance (A)."
 After clicking on "Begin," click "Simulate" in the next
screen you see. By doing this, you'll produce data that will
be analyzed to see if a statistically significant difference
exists between the mean of a sample drawn from Population
A and the mean of a sample drawn from Population B. Whether
your result is "Significant" or "Not significant" will be
shown in this screen's upper righthand corner.
 Now, change the mean of Population B from 15 to 10.001.
By doing this, you've made the 2 population means different,
but different by only a VERY TINY amount. In other words,
the null hypothesis (of equal population means) is false,
but it's false to only a very trivial degree.
 Click the "Reset" button that's above the gray box.
 In the top row of windows, change "n" from 8 to 30, change
the mean for Population B from 15 to 10.001, change the "Population
rho" from 0.5 to 0.999, and change "Population sd" from 5
to .01.
 Click "Simulate" to see if the sample means from the nearly
identical populations are significantly different. If so,
you've just proven to yourself that it's possible for the
hypothesis testing procedure to yield a statistically significant
result when the null hypothesis is "off" by the tiniest of
margins. What you produced was a statistically significant
result . . . but it had NO practical significance. In other
words, what you created was the illusion of a "mountain" when,
in reality, what existed was only a tiny little molehill.
 Sky Huck's Puzzle Question:
Repeat Steps #3 and #4, but this time make the mean of Population
B equal to 10. Before clicking on "Simulate 5000" to replicate
your study 5,000 times, make a guess as to what the "Percent significant"
number will be. After making your guess, click on "Simulate 5000"
to see what happens.

Practical
vs. Statistical Significance (B) 
 Description:
Although this site is noninteractive, it contains a simple example
designed to show that "statistical significance" does not necessarily
imply "practical significance."
 What to Do:
 Click on the colored title of this online resource: "Practical
vs. Statistical Significance (B)."
 Read carefully what's said on each screen, moving from one
screen to another by clicking on the "Next" buttons.
 You'll come across several words that are links to brief
but helpful explanations of what a term means. Don't pass
up the opportunity to gain a handle on these terms by using
the available links.
 Sky Huck's Puzzle Question:
Look at the picture displayed on the 2nd of the 4 pages of this
online resource. Are you looking at confidence intervals?

