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From: zyp9 on 16 Oct 2009 13:55
Has anyone operationalized Liddell's exact SMR from his '84 paper?

Liddell FD. Simple exact analysis of the standardised mortality ratio.
Journal of Epidemiology and Community Health 1984;38:85-88.


I need to operationalize his formula for confidence limits when observed
events are < 15 (p.86), which uses values from a chi-sq table he
mentions as Biometrika Tables for Statisticians. I don't have this
can't replicate his p values in SAS.

I have already found the CLs for obs events > 15, but not for the <15
group:

From Liddell's paper (ex. 1)

%let alpha = 1.645 ;
%let obs = 8;
%let exp = 3.59;

data x;
OBS = &obs ;
EXP = &exp ;
SMR = obs/exp ;

if &obs > 15 then do;
SMR_L = (obs/exp) * (1 - (1/(9*obs)) - (&alpha/(sqrt(9*obs)))
)**3;
SMR_U = ((obs+1)/exp) * (1 - (1/(9*(obs+1))) +
(&alpha/(sqrt(9*(obs+1)))) )**3;
else do;
?


p = ?;
run;


Thanks.
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