topic Re: Test of differences (count) in Statistical Procedures

Test of differences (count)

yoyong555 — Sun, 22 Dec 2019 21:44:12 GMT

Hi everyone.

The scenario is this:

In a trial, a person visits the center thrice. During each visit, the number of medicines he receives is counted.

Example:

Baseline 6 months 1 year

Person 1 9 2 6

I want to know if there is a significant difference in the number of medicines he received across three visits. What statistical test do I use? And how should I program it?

Thank you very much.

Happy holidays to everyone.

Test of differences (counts)

yoyong555 — Sun, 22 Dec 2019 22:00:23 GMT

Hi everyone.

The scenario is this:

In a trial, a person visits the center thrice. During each visit, the number of medicines he receives is counted.

Example:

Baseline 6 months 1 year

Person 1 9 2 6

I want to know if there is a significant difference in the number of medicines he received across three visits. What statistical test do I use? And how should I program it?

Thank you very much.

Happy holidays to everyone.

Re: Test of differences (counts)

PaigeMiller — Sun, 22 Dec 2019 22:11:38 GMT

It is impossible to determine what statistical test to use, or even IF there is a statistical test in this case, without further information.

Is the variability from time period to time period, or across individuals (which doesn't exist as you specified a single person in your example)? Is baseline equivalent to six months or a year or longer? What is the exact (please be specific) hypothesis you want to test? What should we assume is the statistical distribution of this data (normal, Poisson, binomial, other)???

Re: Test of differences (count)

PaigeMiller — Sun, 22 Dec 2019 22:08:42 GMT

Duplicate question, please reply in the other thread. https://communities.sas.com/t5/SAS-Programming/Test-of-differences-counts/td-p/613453

DO NOT REPLY HERE

Re: Test of differences (counts)

yoyong555 — Sun, 22 Dec 2019 23:09:30 GMT

Thanks @PaigeMiller

Re: Test of differences (count)

Kurt_Bremser — Mon, 23 Dec 2019 07:52:04 GMT

I merged the two posts, and moved everything to Statistical Procedures.

Re: Test of differences (count)

StatDave — Mon, 06 Jan 2020 16:14:03 GMT

If there are multiple people and you want to compare the times, then you can arrange your data with one measurement per observation (row) in your data set, and fit a Poisson GEE model similar to what is shown in the example titled "Log-Linear Model for Count Data" in the GENMOD documentation. That example has an offset which you don't appear to have in this case, so the OFFSET= option will not be needed.