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Old June 26th, 2009, 12:56 PM
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Default Chi square test

According to a theory, four categories of strawberries are supposed to occur in the ratio 9:3:3:1. For these four categories, 124, 30, 43 and 11 were counted, respectively. Are these compatible with the theory?Let \alpha=0.05.

Work so far-
124+30+43+11=208

Expected values are therefore 117, 39, 39, 13 for the ratio 9:3:3:1

(4 columns - 1)=3 degrees of freedom

I calculated the Chi-test statistic by doing (124-117)^2/117+....+(11-13)^2/13 and got 3.21, but I am not sure what to compare it to or what to do with the \alpha=0.05. Thanks for your help!

Last edited by larz; June 26th, 2009 at 03:06 PM. Reason: More work
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Old June 27th, 2009, 02:42 AM
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Quote:
Originally Posted by larz View Post
According to a theory, four categories of strawberries are supposed to occur in the ratio 9:3:3:1. For these four categories, 124, 30, 43 and 11 were counted, respectively. Are these compatible with the theory?Let \alpha=0.05.

Work so far-
124+30+43+11=208

Expected values are therefore 117, 39, 39, 13 for the ratio 9:3:3:1

(4 columns - 1)=3 degrees of freedom

I calculated the Chi-test statistic by doing (124-117)^2/117+....+(11-13)^2/13 and got 3.21, but I am not sure what to compare it to or what to do with the \alpha=0.05. Thanks for your help!
df = 4 - 1 = 3.

Critical value for 3 df at 0.05 significance level is 7.81 (got from tables).

3.21 < 7.81 therefore ......
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Old June 27th, 2009, 07:40 AM
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Therefore the observations are compatible with the theory! Thanks. I found the table you are talking about. Now it makes sense.
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