Complex BINOMDIST function

[swimmychic]

trying to work through experiment data, I am trying to find smallest n (# study subjects at start of study) that will allow a 96 percent chance of having at least 75 subjects (m=75) remaining at end of the study. there's a 90 percent chance that the subject will remain in the study (p= 0.9).

the range of possible n's (subjects) is 75-100

tried using =BINOMDIST(75,75,.9,1) to find the chance for n=75 that there are at least 75 subjects remaining in the study at the end... but no results. is there a way to manipulate the formula that i'm missing?

[shg]

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The formula for the first line calculates the probability of having at most at most 25 failures in 100 trials when the probability of failure is 10%.

For 89 subjects (trials), the probability of at most 14 failures (leaving 75) is 96.9%