• We are pleased to announce that the winner of our Feedback Prize Draw for the Winter 2024-25 session and winning £150 of gift vouchers is Zhao Liang Tay. Congratulations to Zhao Liang. If you fancy winning £150 worth of gift vouchers (from a major UK store) for the Summer 2025 exam sitting for just a few minutes of your time throughout the session, please see our website at https://www.acted.co.uk/further-info.html?pat=feedback#feedback-prize for more information on how you can make sure your name is included in the draw at the end of the session.
  • Please be advised that the SP1, SP5 and SP7 X1 deadline is the 14th July and not the 17th June as first stated. Please accept out apologies for any confusion caused.

Ct3:chap 12

S

Shikha Agarwal

Member
On page 30: accuracy of chi square aproximation,
.
It is mentioned that:
(However,the statistic is more robust than that and in practice a less conservative approach,such as ensuring that all ei's are greater than 1 and that not more than 20% of them are less than 5, may be taken)
.
What does this line means?
 
The requirement of chi-square test is that all expected values should be more than 5, however this is a loose requirement. So even if few expected values (not more than 20%) are less than 5, results of the test would still be valid.
There are other tests which can be used when these requirements are not met. See these links

https://www.researchgate.net/post/I...at_is_the_appropriate_statistical_test_to_use

http://stats.stackexchange.com/ques...st-if-many-cells-have-frequencies-less-than-5

So it means if less than 20% expected values are less than 5, then only we combine?
 
So it means if less than 20% expected values are less than 5, then only we combine?
In Ct-3 we combine for all expected values less than 5. But even if few expected values are less than 5 (as long as they're less than 20%), we can carry on with the test.
For this exam, just combine to make all expected values greater than or equal to 5.
 
Back
Top