Ct3:chap 12

[Shikha Agarwal]

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?

 

[suraj]

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

 

[Shikha Agarwal]

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?

 

[suraj]

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.

 

[Shikha Agarwal]

Thnq!