Other's OnLine Resources (Chapter 17)
2x3
Chi Square 
 Description:
This interactive online resource gives you the chance to (a)
change the cell frequencies in a 2x3 contingency table and then
(b) see what the chisquare calculated value and accompanying
plevel are for your data.
 What to Do:
 Click on the colored title of this online resource: "2x3
Chi Square."
 On the screen that pops up, scroll down (if you need to)
until you see a rectangle containing 3 rows ("Male," "Female,"
and "Total") and 4 columns ("White," "Black," "Hispanic,"
and "Total").
 Click on each of the cells in the contingency table (but
not on those in the "Total" row or column) and change the
numbers.
 Click on the "Compute!" button, and then examine the numbers
in the "Chi square" and "plevel" boxes.
 Repeat Steps 3 and 4 several times until you get a feel
for the kinds of data sets that cause p to be large or small.
 Sky Huck's Puzzle Question:
It's possible to fill the 6 cells of the 2x3 contingency table
with 6 different numbers and yet have p turn out equal to 1, thus
indicating the the sample data are perfectly aligned with the
null hypothesis. Can you do this?

Tests
of Proportions 
 Description:
In using this interactive online resource, you'll be able to
simulate what happens when a onesample test of a proportion is
used. After exerting control over what the null hypothesis says
and several other important things (such as the nature of the
alternative hypothesis and the level of significance), you'll
get to see a visual display of the results when 100 random samples
are evaluated.
 What to Do:
 Click on the colored title of this online resource: "Tests
of Proportions."
 Scroll down to the gray horizontal bar that is positioned
above a wide pink rectangle.
 Click on the "Play" button that's located near the right
end of the gray bar.
 Examine the information that's presented above, in, and
below the pink bar so as to get a feel for what's going on.
 Each of the tests you just conducted was onetailed in nature.
Repeat the simulation, this time in a twotailed fashion;
to do this, choose the bottom option in the pulldown menu
near the left end of the gray bar. Then, click the "Play"
button.
 Make changes in (a) the null number in the "p0" box (so
it's something other than .5), (b) the value of the population
proportion in the "p" box (so it's something other than .5),
and (c) the level of significance. After each change you make,
click on the "Play" button to see what happens.
 Sky Huck's Puzzle Question:
What is the meaning of the exclamation point that appears in one
of the "Ha" options in the gray bar?

Chi
Square and Yates 
 Description:
In using this interactive online resource, you'll be able to
(1) see how the Yates correction makes the chisquare test more
conservative and (2) investigate for yourself whether the Yates
correction is too conservative.
 What to Do:
 Click on the colored title of this online resource: "Chi
Square and Yates."
 After clicking on "Begin," you'll get a new screen that
has 3 gray boxes. In the upper lefthand box, you'll see that
the probability for success is 0.6 for both of the two hypothetical
conditions being compared. With both probabilities the same,
the null hypothesis is true.
 Click on "Simulate 1" to see, in the two gray boxes on the
right, what happens when sample data are extracted from the
hypothetical populations and analyzed by a chisquare test,
both with and without the Yates correction.
 Now click on "Simulate 5000" to see, in the lower righthand
box, what would happen over 5,000 replications. Of course,
with the significance level set at 0.05 (see upper righthand
box) and with the null hypothesis being true, 5% of the results
should be significant.
 Sky Huck's Puzzle Question:
Change the 2 values of "N" in the upper lefthand box from 10
to 20. Now, with larger sample sizes, what do you think the "Proportion
significant" number will be if you click "Simulate 5000"? Click
and see. Then increase N again and repeat the simulation. What
do you see happening?

Fisher's
Exact Test 
 Description:
In using this interactive online resource, you'll be able to
enter data into a 2x2 contingency table and then see the plevel
that's computed for your data. By entering various combinations
of hypothetical data, you'll come to understand why a Fisher's
Exact Test sometimes leads to a statistically significant result.
 What to Do:
 Click on the colored title of this online resource: "Fisher's
Exact Test."
 On the screen that pops up, locate the 4 open boxes labeled
"a," "b," "c," and "d."
 Imagine that boxes "a" and "b" represent the number of males
who did and didn't get at least 1 traffic ticket during the
past 6 months. Likewise, imagine that boxes "c" and "d" represent
the number of females who did and didn't get at least 1 traffic
ticket during the past 6 months.
 Enter the number 5 in each of the 4 boxes and then cliock
"Please Calculate Now." Look at the plevel that's displayed
on the next screen that pops up.
 Click on your browser's "back" button, repeat Step #4 with
different numbers going into the 4 cells, and then repeat
this process several times until you get a "feel" for what
kinds of data sets cause Fisher's Exact Test to yield small
plevels.
 Sky Huck's Puzzle Question:
Suppose you were to begin with the number 2 in each of the 4 cells
of the 2x2 contingency table. Further suppose that you now could
do one of two things: (1) add 5 to cell "b" and add 5 to cell
"c" OR (2) add 10 to cell "b." Which of these changes do you think
would lead to the smaller plevel? After making your guess, make
both changes, examine the 2 plevels, and see if your guess was
correct.

