# Thread: 2-Group comparison on proportions?

1. ## 2-Group comparison on proportions?

I work at a company that has full-time and part-time employees. Sometimes we have to ask people to come to work on a day off. We offer generous compensation for that.

There is a belief that some employees opt to work part-time to then wait to be called on a day off to work, and thereby increasing their pay significantly.

We are chronically short staffed, so we "buy" many days off per month.

What is a good way to test the 2 groups to see if there is a difference?

I have attached a sample file.

I have 2 types of data:
1. % of full-time employees and % of full-time employees that sell a day off (and thereby also part-time)
2. A list of employee names and ONLY the dates that they sold a day off (i.e. not for every day of the month, just those days they sold a day off). If they didn't sell a day off in the month their name does not appear on the list.

I guess a simple t-test could do it. I would just have to fill in the data per day per month per employee I guess.

Any other methods out there? Can I use the proportions?

2. ## Re: 2-Group comparison on proportions?

If you had only one month you could do a chi-square to assess the association between full and part time with whether or not the employee sold a day off. I assume you are making that yes/no for a given month. Of course you have to work with raw numbers, not percentages, for the analysis. Across a number of months, what about something like a Mantel-Haenszel pooling with month as the stratum?

3. ## Re: 2-Group comparison on proportions?

I am interested in seeing if there is a difference between full and part-time tendencies to sell a day off.

I have a hunch that there is no statistical difference between the number of days off that full vs part time sell.

4. ## Re: 2-Group comparison on proportions?

You should be able to use the 2-proportions test. https://onlinecourses.science.psu.edu/stat414/node/268

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