topic Re: not the correct expected proportion in Statistical Procedures

not the correct expected proportion

PSIOT2 — Thu, 04 Dec 2025 07:26:21 GMT

Hi,

I am trying to calculate the Hosmer-Lemeshow p-value using proc logistic with lackfit option but the expected proportion given by SAS are not mine. How to put the expected proportion in the model?

Please find my code:

proc logistic data=noduleData;
model GT_finding(event='1')= report_score/ lackfit (DF=8 NGROUPS=13034 321 338 77 80 151 109 86 73 36 ) ;
run;

Thank you

Re: not the correct expected proportion

Ksharp — Thu, 04 Dec 2025 09:43:24 GMT

Could you explain your issue more clear ?

According to the Documentation:

So you could check the output of logistic model is right or not.

Code something like:

proc logistic data=sashelp.heart(obs=1000 where=(height is not missing));
model status(EVENT='Dead')=height /lackfit(DF=8 NGROUPS=10) ;
output out=want p=pred;  *save predicted Prob for dividing groups in Hosmer-Lemeshow test;
run;



/********Check the expected proportion is matched or not*************/
proc rank data=want out=want2 groups=10 ;
var pred;
ranks groups;
run;
proc sql;
select groups,count(*) as count,sum(Status = 'Dead' ) as Status_Dead_Obs,sum(pred) as Expected
from want2
 group by groups;
quit;

Here I take Status = 'Dead' as an example . and get the correct expected proportion.

Here I think the most different thing is how to split these data into groups . Check the Doc ,see H-L how to group these data, once you know the details of H-L, I believe you would get the matched result.

Re: not the correct expected proportion

PSIOT2 — Thu, 04 Dec 2025 09:53:55 GMT

Thank for your answers.

I have 10 groups with proportion expected = 0.0003, 0.01, 0.02, 0.06, 0.18, 0.29, 0.39, 0.71, 0.89, 0.93.

The number of cases in each groups are different too: 13034, 321, 338, 77, 80, 151, 109, 86, 73, 36.

It seems that it is not possible to precise to enter the expected proportions in logistic model.

Re: not the correct expected proportion

Rick_SAS — Thu, 04 Dec 2025 21:23:56 GMT

Where are the sizes 13034 321 338 77 80 151 109 86 73 36 coming from?
The doc discusses how to get the observed and expected numbers for the groups in the H-L test.
Please run your model as

proc logistic data=noduleData;
model GT_finding(event='1')= report_score/ lackfit (DF=8 NGROUPS=10) ;
ods select  LackFitPartition;
run;

and upload the LackFitPartition table for your data.

Re: not the correct expected proportion

Ksharp — Sat, 06 Dec 2025 12:20:14 GMT

I think Rick is right.
According to Doc ,the group number is balance(a.k.a has almost the same number in each group), you can not get unbalance group .
Check the Doc again.

Re: not the correct expected proportion

PSIOT2 — Mon, 08 Dec 2025 12:53:06 GMT

Please find the LackFitPartition:

Re: not the correct expected proportion

Ksharp — Mon, 08 Dec 2025 13:03:30 GMT

You have extreme unbalance data:
367: 13938 =0.026
a.k.a the probability of event is too small.
Logistic model is unsuited(not right) for this data.
You need to oversample data to make this ratio is about 0.1, 0.2 ,0.3 .... and use PROC LOGISTIC again.
Or try other model like : Decision Tree, Random Forest .

Re: not the correct expected proportion

Ksharp — Wed, 10 Dec 2025 05:47:11 GMT

Here is the issue I am talking about.
https://support.sas.com/kb/22/601.html

Re: not the correct expected proportion

PSIOT2 — Wed, 10 Dec 2025 07:41:38 GMT

Thank you, proc logistic is not appropriate with this dataset.