In: Statistics and Probability
Here probability of high school graduation rate = p = 0.80
sample size = n= 20
as the events are independent and success rate is constant.
So here if x is the the number of graduates out of 20, so x will have binomial distribution with parameter n = 20 and p = 0.80
(A) So here the distribution
p(x) = 20Cx (0.80)x(0.20)(20 - x)
p(x = 17) = 20C17(0.80)17(0.20)3 = 0.2054
(B) Probability that 16 or fewer willgraduate
Here we will use cumulative binomial function either in excel (BINOMDIST) or in TI-84 calculator (BINOMCDF)
Pr(x 16) = BINOMDIST(x 16;20 ;0.80) = 0.5886
(C) Probability that at least 17 high school studnets in our sample of 20 will graduuate.
Pr(x 17) = 1 - Pr(x 16)
Pr(x 17) = 1 - 0.5886 = 0.4114