AP Statistics
posted by Laura on .
Of all U.S. fourth graders, 71% are assigned mathematics homework three or more times per week. If 5 fouth graders are randomly selected to be checked for this frequency of homework assignment during a randomly chosen week, find the probability that
A.) exactly one fourth grader was assigned homework three or more times that week
B.) no fourth grader was assigned homework three or more times that week
C.) at least one fourth grader was assigned homework three or more tiems that week

a)
NNNNY
NNNYN
NNYNN
NYNNN
YNNNN
so, there are five ways to sort the fourth graders
Pr(one)=5*.71*.29^4=.0251 check that.
b)Pr(none)=.29^5
c) Pr(at least one)=1Pr(none) 
A. .0251
B. .0020
C. None