distribution r studio – Cross Validated

About 12% of males are colorblind. A researcher needs three colorblind men for an experiment and begins checking potential subjects. What is the probability that she finds exactly 3 or 4 men in the first 7 trials she examines? The average number of colorblind men out of sample size of 7 is equal to 0,84.

if sample zize = 7, and mean = 0,84 => P (x = 3 or 4) equals 2/7 = 0.2857

but why we need mean? and in r studio is binomial probability and i should use pbinom? if im right could u please check

pbinom (3:4, 7, 2/7)
[1] 0.8917264 0.9767250