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# Proc Stdrate how SAS calculate the variance of the rate in the jth stratum of the study population

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Hi,

I'm looking at how SAS calculate the variance of the rate in the jth stratum of the study population, particularly in Example 107.1.

The data provided only gives the aggregated form- so how did they calculate the variance, say the variance of the rate in the group Male, age 0-14 in state of Alaska?

Thank you,

Huong

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‎09-20-2016 03:53 PM
Super User
Posts: 20,715

## Re: Proc Stdrate how SAS calculate the variance of the rate in the jth stratum of the study populati

Flashback to intro stats - SD of a rate is sqrt(p*(1-p)/n)

Here's are the mathematical formulas:

https://support.sas.com/documentation/cdl/en/statug/68162/HTML/default/viewer.htm#statug_stdrate_det...

In general, you have a rate with the N known, and we make assumptions regarding the distribution of said rate. Based on this we can calculate the bounds on the rate using the specific formula's.

And I'll move your post to the Stats Forum so you can get some better answers.

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Solution
‎09-20-2016 03:53 PM
Super User
Posts: 20,715

## Re: Proc Stdrate how SAS calculate the variance of the rate in the jth stratum of the study populati

Flashback to intro stats - SD of a rate is sqrt(p*(1-p)/n)

Here's are the mathematical formulas:

https://support.sas.com/documentation/cdl/en/statug/68162/HTML/default/viewer.htm#statug_stdrate_det...

In general, you have a rate with the N known, and we make assumptions regarding the distribution of said rate. Based on this we can calculate the bounds on the rate using the specific formula's.

And I'll move your post to the Stats Forum so you can get some better answers.

New Contributor
Posts: 2

## Re: Proc Stdrate how SAS calculate the variance of the rate in the jth stratum of the study populati

Thank you! I was a bit confused since the support file didn't specify the Poisson assumption....

☑ This topic is solved.