AP STATISTICS
Quiz-6.3b Geometric Random Variables
Last 4 of Student ID____________
Period______
1. Research suggests that about 24% of 12-year-olds in the United States can pick out the state of
Colorado on a map.
(a) What is the probability that you must sample exactly 5 twelve-year-olds to find the first one
who can pick out Colorado on a map?
P(X=5) geometpdf(.24,5)=0.0801
(b) What is the probability that you must sample 5 or more twelve-year-olds to find the first one
who can pick out Colorado on a map?
P(X≥5) 1-geometcdf(.24,4)=0.3336
2. Suppose that 20% of a herd of cows is infected with a particular disease.
(a) What is the probability that the first diseased cow is the 3rd cow tested?
P(X=3) geometpdf(.2,3)=0.128
(b) What is the probability that 4 or more cows would need to be tested until a diseased cow was
found?
P(X≥4) 1-geometcdf(.2,3)=0.512