Table of Contents

• Prequiz...
• 1: Do those shoes fit?
• 2: Dilbert's 3 day work week
• 3: The day is saved . or not
• 4: The Brute Force method
• 5: Computer = brute force
• 6: What's your threshold for pain?
• 7: Sick-day sistribution
• 8: A brief recap of the Brute Force Method
• 9: The Brute Force method again
• 10: Using arithmetic instead of Brute Force
• 11: One small correction
• 12: How big is big?
• 13: Degrees of Freedom
• 14: The magic lookup table
• 15: The answer, finally
• 16: Summary of chi-square
• 17: Another example for chi-square
• 18: So, which method do you like better?
• 19: Applications
• 20: Example 1: Testing for a dihybrid ratio
• 21: Example 2: Habitat selection (ecology)
• 22: Review and Words of Wisdom

Another example for chi-square:

Once again the Evil Pointy-Haired Boss has been accused of cheating at dice. In the last game, he had the following rolls:

number on dice	1	2	3	4	5	6
how many times	1	2	2	4	4	5

How likely is it that the dice are fixed? You can use the chi-square table below:

	observed ("o")	expected ("e")	(o-e)	(o-e)2	(o-e)2/e
roll of 1
roll of 2
roll of 3
roll of 4
roll of 5
roll of 6
Total	18	18
Check

Ok, so now take that calculated chi square value and compare it to the critical chi square on the table.

So, because your chi-square calc is less than your chi square crit, you fail to reject your null hypothesis -- and your verdict? Well, your verdict is that your boss does not cheat (at least when it comes to dice).