topic Re: Fisher’s ex in Statistical Procedures

Fisher’s ex

sumah — Mon, 27 Sep 2021 19:54:33 GMT

Any clue when is Fisher’s exact test invalid or in other words, when it can NOT be used? I’m getting a warning message about % of missing data in the SAS output but couldn’t figure it out! I used proc freq

Re: Fisher’s ex

pink_poodle — Mon, 27 Sep 2021 20:04:38 GMT

Could you please write what it says in the warning message?

Re: Fisher’s ex

sbxkoenk — Mon, 27 Sep 2021 20:10:24 GMT

Hello,

Can you present us with the exact warning message?

Is it a WARNING in the LOG or in the OUPUT / RESULTS??

I understand SAS is complaining about missing values in your data set, not about frequency counts that are zero nor about other sparsity in the data, correct?

Thanks,

Koen

Re: Fisher’s ex

sumah — Mon, 27 Sep 2021 21:17:40 GMT

Re: Fisher’s ex

sumah — Mon, 27 Sep 2021 21:20:24 GMT

Re: Fisher’s ex

sumah — Mon, 27 Sep 2021 21:25:33 GMT

Re: Fisher’s ex

sbxkoenk — Mon, 27 Sep 2021 21:40:17 GMT

Hello,

That "warning" in the results is just to make you aware that not all your observations were used in the PROC FREQ Fisher's exact test as not all your observations can be counted (some observations have missing values for the row and / or column variable in your contingency table).

It does not mean that the Fisher's exact test is invalid.

It is valid but not all observations participated in the analysis!

Koen

Re: Fisher’s ex

sumah — Mon, 27 Sep 2021 21:46:40 GMT

I see! I usually use Fisher's test and that was the first time I get a warning and in the output, not the log. Thank you so much!!!

Re: Fisher’s ex

Ksharp — Tue, 28 Sep 2021 12:39:25 GMT

That said ChisquareTest is not valid, NOT Fisher Exact Test !
ChisquareTest and Fisher Exact Test is totally different !

Re: Fisher’s ex

sbxkoenk — Tue, 28 Sep 2021 14:18:19 GMT

Thanks for pointing that out @Ksharp .
indeed, an important addition on your part!

Koen

Re: Fisher’s ex

sumah — Tue, 28 Sep 2021 15:33:44 GMT

I started with ch-squared and it wasn't valid so I switched to Fisher's test

Re: Fisher’s ex

Ksharp — Wed, 29 Sep 2021 12:20:02 GMT

But you said:
"Any clue when is Fisher’s exact test invalid "

You can always use Fisher Test as long as it is displayed .

Chisq Test require 5% count in each cell as least .

Re: Fisher’s ex

sumah — Wed, 29 Sep 2021 15:33:42 GMT

yes, that was my question, I thought at first I can't run a fisher's exact test but found out it's okay. thanks again.