Chi-Square Goodness Of Fit Test
CONCEPT:
• Used for checking frequency distributions
Remember:
Rolling a Die:
Outcome X
1
2
3
4
5
6
Probability P(X)
1/6
1/6
1/6
1/6
1/6
1/6
A discrete probability distribution consists of the values a random variable can assume
and the corresponding probabilities of the values.
If you roll the following:
Rolling a Die:
Outcome X
1
2
3
4
5
6
Frequency
8
6
9
8
7
2
Is the die lopsided?
Formula for the Chi Square Goodness Of Fit Test
χ2 =
(O−E)2
E
∑
Where
• O = observed frequency
• E = expected frequency
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