In the DISTR menu, we have two binomial functions, binompdf and binomcdf.. The i
ID: 3208933 • Letter: I
Question
In the DISTR menu, we have two binomial functions, binompdf and binomcdf.. The inputs for each is the same:
n = number of trials, p = probability of success, X = # of successes.
But binompdf is the binomial probability distribution function, and binomcdf is the binomial cumulative distribution function. That is,
P(X = k) = binompdf (n, p, k) is the probability of exactly k successes
in n trials.
P(X < k) = binomcdf (n, p, k) is the probability of at most k successes
in n trials.
Suppose we have a binomial distribution with n = 20 and p = 0.43, and find the following probabilities.
a) P(X = 12)
b) P(X > 7)
c) P(X < 15)
Explanation / Answer
a) P(X= 12)
= binompdf (20, 0.43, 12)
= 0.0561
b) P(X > 7)
= 1 - P(X <= 7)
= 1 - binomcdf (20, 0.43, 7)
= 1 - 0.3132
= 0.6868
c) P(X < 15)
= P(X <= 15) - P(X = 15)
= binomcdf (20, 0.43, 15) - binompdf (20, 0.43, 15)
= 0.9992 - 0.003
= 0.9962