# Chi-squared testsWatch

#1
For 7b one of the expected frequencies is less than 5 so why haven’t they pooled the Variables before they worked out X^2?
https://imgur.com/a/zvKU3f5
0
4 weeks ago
#2
It's if more than 20% of the expected results are less than 5 then you pool together.
You only always pool results together when the expected frequency is less than 1
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#3
(Original post by AzureCeleste)
It's if more than 20% of the expected results are less than 5 then you pool together.
You only always pool results together when the expected frequency is less than 1
I’m not sure where you’ve got these figures from? The textbook doesn’t mention anything like that and the CGP guide says “all expected values must be at least 5”
0
4 weeks ago
#4
(Original post by Y12_FurtherMaths)
I’m not sure where you’ve got these figures from? The textbook doesn’t mention anything like that and the CGP guide says “all expected values must be at least 5”
That's how I was always taught it. I was on a different exam board but we were taught only to combine groups together if more than 20% of the expected frequences were less than 5 or if they were less than 1
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#5
(Original post by AzureCeleste)
That's how I was always taught it. I was on a different exam board but we were taught only to combine groups together if more than 20% of the expected frequences were less than 5 or if they were less than 1
Are you able to explain the difference between these two formulas? Because I don’t really understand what the second one means https://imgur.com/a/b2n1kgR
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4 weeks ago
#6
(Original post by Y12_FurtherMaths)
Are you able to explain the difference between these two formulas? Because I don’t really understand what the second one means https://imgur.com/a/b2n1kgR
They're the same?
One's just saying that it is approxiametly the same as X^2v
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#7
(Original post by AzureCeleste)
They're the same?
One's just saying that it is approxiametly the same as X^2v
Right I see thanks. Tagging RDKGames as I’m still unsure on the pooling issue
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4 weeks ago
#8
(Original post by Y12_FurtherMaths)
Right I see thanks. Tagging RDKGames as I’m still unsure on the pooling issue
https://en.wikipedia.org/wiki/Pearso...i-squared_test

It's explained here if you go down to expected cell count under assumptions
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#9
(Original post by AzureCeleste)
https://en.wikipedia.org/wiki/Pearso...i-squared_test

It's explained here if you go down to expected cell count under assumptions
It sort of makes sense, but idk if that’s just for Edexcel? I think that’s the exam board since I’m on AQA and all it says for me is just “greater than 5”
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4 weeks ago
#10
(Original post by Y12_FurtherMaths)
It sort of makes sense, but idk if that’s just for Edexcel? I think that’s the exam board since I’m on AQA and all it says for me is just “greater than 5”
It will vary from exam board to exam board.
Are the questions you doing specific to your exam board or not?
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#11
(Original post by AzureCeleste)
It will vary from exam board to exam board.
Are the questions you doing specific to your exam board or not?
It doesn’t specifically specify they are AQA based questions but one would assume so since they’re taken from a mixed practice section in the AQA textbook
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