Question 921933
Re TY, Yes, TY,  p = .10
p(undesirable side effects) = .10,  n = 12
P(x ≤ 2) = binomcdf(12, .10, 2)= .8891  0r 88.91% Using TI
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One could also Use Your Casio fx-115 ES plus  0r fx-991 ES plus  
In a similar fashion: Mode: DIST(binomial CD).
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Recommend Using stattrek.com to check  Results
until You are familiar with Using Your Calculator.
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Above by hand:
P(x ≤ 2) = P(0) + P(1) + P(2) 
where: {{{P (x)= highlight_green(nCx)(p^x)(q)^(n-x) }}} 
p = .10, q = .90 and n = 12