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+--- Thread: HP50G - Binomial Test Statistics (/thread-16379.html)
HP50G - Binomial Test Statistics - cjmcc - 02-25-2021 03:45 PM
I'm working my way through some test statistics, trying to recreate everything on my HP for fun and to improve my understanding. Stat49 Pro has been a great help providing inverse statistical distributions.
My problem is determining the confidence bounds for some pass/fail tests. The example has 9 successes out of 10 trials. The point estimate for reliability is 0.9, but finding the 80% confidence bounds gets a little messier. The 'approved' method used the BETAINV function in Excel. Poking around on the web showed the Clopper-Pearson method can also provide the upper and lower reliability bounds using the cumulative inverse F distribution. So far, so good.
Stat49 Pro happily determines F(20.2.0.1)=9.44 which leads to an upper reliability bound of 0.99 (matching the example). But when I try to find the lower bound, Stat49 Pro claims F(18,4,0.9)=-2.19E70 instead of the expected 0.44 to provide the 0.66 lower bound.
Does anyone know why Stat49 Pro freaked out? Checking an on-line F distribution calculator gives the expected result and asking the HP50g : 18 4 0.44 UTPF gets 0.90 as expected.
-Chris-
Ref:
https://www.liquisearch.com/binomial_proportion_confidence_interval/clopper-pearson_interval