According to the Us Census Bureau, in 2007 about 10% of persons between 25 and 30 years old live alone. Let S be the event a person lives alone. If five persons in that are group are randomly selected, a) Find the probabilty of the sequence SFFSF. b) Find the probability of exactly 2 S\'s. Solution a) p = 0.1 * 0.9 * 0.9 * 0.1 * 0.9 = 0.00729 b) p = 5C2 * ( 0.1 )^2 * ( 0.9 ) ^3 = 0.0729.

1. According to the Us Census Bureau, in 2007 about 10% of persons between 25 and 30 years old
live alone. Let S be the event a person lives alone. If five persons in that are group are randomly
selected,
a) Find the probabilty of the sequence SFFSF.
b) Find the probability of exactly 2 S's.
Solution
a) p = 0.1 * 0.9 * 0.9 * 0.1 * 0.9 = 0.00729
b) p = 5C2 * ( 0.1 )^2 * ( 0.9 ) ^3 = 0.0729