
The
Public Health Disparities Geocoding Project Monograph 

Geocoding
and Monitoring US Socioeconomic Inequalities in Health: An introduction to using areabased socioeconomic measures 
WHY? 
READ
MORE 
HOW
TO 
TRY
IT OUT! 
TOOLS 

STEP
BY STEP COMPARISON 

Step
6: Estimate the agestandardized incidence rate ratio comparing the age standardized rates in each poverty stratum to the rate in the least impoverished poverty stratum (04.9%). 

SAS
PROGRAMMING click here to download SAS program 

Calculate the 95% confidence limits on the incidence rate ratio.  3.
Confidence
intervals for IR 
DATA
Step6 ; SET Step5c ; RETAIN IRREF VARPYREF ; IF _N_=1 THEN DO ; IRREF=IRW ; VARPYREF=VARPYW ; END ; ************************************ L_IRD=IRD  (1.96
* SQRT(VARIRD)) ; L_IRR=EXP(LOG(IRR)
 (1.96 * SQRT(VARIRR))) ; RUN ;

where y is the count, i.e. zero. When =0.05 (i.e. for a 95% confidence limit) this simplifies to  
3.689.  
We can then divide this upper limit on the count by the population denominator to give the upper limit on the rate.  
4.
Agestandardized incidence rate ratio To compare
two agestandardized incidence rates on the absolute scale, the agestandardized
incidence rate difference (IRD 

To
compare agestandardized rates from two different groups or regions on
the relative scale, the agestandardized incidence rate ratio (IRR 

This
work was funded by the National Institutes of Health (1RO1HD3686501)
via the National Institute of Child Health & Human Development (NICHD)
and the Office of Behavioral & Social Science Research (OBSSR). 

Copyright
© 2004 by the President and Fellows of Harvard College  The Public
Health Disparities Geocoding Project. 