Understanding Basic Statistics 6th Edition by Charles Henry Brase,Corrinne Pellillo Brase

Exercise 21

Sociology: Dress Habits A research team at Cornell University conducted a study showing that approximately 10% of all businessmen who wear ties wear them so tightly that they actually reduce blood flow to the brain, diminishing cerebral functions (Source: Chances: Risk and Odds in Everyday life. by James Burke). At a board meeting of 20 businessmen, all of whom wear ties, what is the probability that
(a) at least one tie is too tight
(b) more than two ties are too tight
(c) no tie is too tight
(d) at least 18 ties are not too tight