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Hans_Hsu
Occasional Contributor

Sample size and baseline data size

I'm using sample size and power for "count per unit"  in JMP, and one question come up my mind

 

For sample size, I  know I can get guideline after I key in power and difference to detect.

But for baseline, is there any guideline how many data point is recommanded to determine baseline? (too many will be waste of time for me) 

 

For example, in my case:

Baeline data point I collected Mean value
501.29
2501.67
3501.53

 

 

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phil_kay
Staff

Re: Sample size and baseline data size

Sorry. I don't understand your table. What are the Mean values?

Baseline Count per Unit is your estimate of what is the typical counts per unit. This is required as part of the power analysis. When you have the baseline it is then possible to determine the power to detect a given difference from that baseline for given sample size. Or you can calculate the required sample size for a given different to detect and power (as you said).

I suggest you try different estimates for Baseline and look at the effect on the sample size estimate.
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