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# MEI S3 chi squared - combining catagories watch

1. i thought we only need to combine when the expected frequency is below 5. but then in Jun 08 question 4, the mark scheme combined the catagories even when the expected frequency is 5.55.

why??

http://www.mei.org.uk/files/papers/s308ju_yfw8.pdf
2. (Original post by freakynerdlol)
i thought we only need to combine when the expected frequency is below 5. but then in Jun 08 question 4, the mark scheme combined the catagories even when the expected frequency is 5.55.

why??

http://www.mei.org.uk/files/papers/s308ju_yfw8.pdf
The two classes above the 5.55 have a combined expected frequency < 5, and so must be merged with the chass with e.f. 5.55

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