t-test for sample comparison
Rick Parcels
kenzie71 at pathcom.com
Sat Nov 15 00:13:22 EST 1997
I have to perform the preparatory test to the microbial limits test (USP)
on all of my company's final products. The method I would like to use to
validate the test is as follows:
Broth/Product mixture is inoculated with 10-100cfu/mL. Mixture is plated
10 times using 1.0 mL. Counts are taken.
Broth/Water mixture is inoculated with 10-100cfu/mL. Mixture is plated 10
times using 1.0 mL. Counts are taken.
These results from these two mixtures (Product and Control) are compared
using a t-test.
Does anyone know if the t-test is the appropriate statistical method to be
using to comapre the results? I learned in school that the t-test can only
be used if the larger variance divided by the smaller variance is < 2. My
ratio is much larger than two. I can't find any other appropriate method
of comparing two population means (or would this be a sample mean?).
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