Contingency Table Cells Associated with Conditional Statements

Below is the contingency table associated with an a sample questionnaire that asks two questions: "Which of three products did you buy?" and "Did you see our advertisement?" The answers to each questionnaire would determine one mark in the empty cells of the table. After all the questionnaires have been counted and the resulting frequencies converted to relative freguencies, these relative frequencies would then be used to find various probabilities. Of course, which table entries to use in determining a probability depends on the wording of the statement that describes the probability.

How to Use the Table

In a table below the contigency table are examples of statements used to describe the probability of intersections, unions, and conditional probability. To the left of each statement is a checkbox. When you check a checkbox, the table is programmed with the location of entries that are used to calculate the probability. You then click inside the cells that you think would be involved. When you click inside a cell, it turns blue. When you have thus marked all of the entries that would be involved in calculating the probability, you click on the button marked "Check Answer". Each cell then changes color according to whether the cell is involved in calculating the probability or not. If you have failed to click on a cell that you should have clicked, the cell turns yellow. If you clicked on a cell that should not have been clicked, it turns red. Cells that were correctly clicked turn green. Of course if you wish to try again click the "clear" button.

Conditional Probabilities

Conditional probabilities are are different from probabilities of intersections and unions. Two table entries are used but they are used differently. One entry is the numerator of the fraction and the other is the denominator. You are supposed to click on the entry used in the numerator first and it will turn blue. Then you click on the entry used inthe denominator and it will turn black. If you reverse them, the cells turn yellow to indicate the error. Remember, if you click on a cell that is not used at all, it turns red on correction.

Summary

This is only one table, but tables only differ in size and labels, so if you succeed with this table you should have no trouble with your own as long as they are constructed correctly. Have fun!

Contingency Table	Did You See Our Ad?2
What Brand Did You Buy?		Saw Ad	Didn't See Ad	Totals
	Brand X
	Brand Y
	Brand Z
	Totals