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Thread: How many tests?

  1. #1
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    How many tests?


    I am trying to bridge a new reagent with an existing one so when the existing one runs out I can use the new one. I want to test the old and new reagent together and then perform a t-test to check if the results are significantly different or not. My question is - how can I calculate how many tests I need to perform to have enough data so my t-test is robust enough? Any help/a calculation would be very helpful!

    Thanks - a very stressed biologist with very limited stats experience!!

  2. #2
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    Re: How many tests?

    You need to look up the sample size calculation for a two sample t-test. You will need to set your alpha (typically 0.05), power (typically 0.80) and have some assumptions about what the minimum difference you want to be able to detect. Many people like to use G-power, I have not used that program. If you plan to run your ttest in a software program, you can see if it providers sample size procedure options as well.
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