Additional Probability Problems

1) The American Red Cross says that about 45% of the U. S 1) The American Red Cross says that about 45% of the U.S. population has Type O blood, 40% Type A, 11% Type B, and the rest type AB. Someone volunteers to give blood, what is the probability that this donor has Type AB blood? has Type A or Type B? has the complement of Type O? 4% 51% 55%

2) The American Red Cross says that about 45% of the U. S 2) The American Red Cross says that about 45% of the U.S. population has Type O blood, 40% Type A, 11% Type B, and the rest type AB. Among four potential donors, what is the probability that all are Type O? no one is Type AB? at least one is Type B? d) they are not all Type A? 0.041 0.849 0.373 0.974

3) A consumer organization estimates that over a 1-year period 17% of cars will need to be repaired only once, another 7% need repairs twice, and another 4% will require three or more repairs. If you own two cars, what is the probability that neither will need repair? both will need repair? .5184 .0784

4) A slot machine has three wheels that spin independently 4) A slot machine has three wheels that spin independently. Each has 10 equally likely symbols: 4 bars, 3 lemons, 2 cherries, and a bell. If you play, what is the probability you get 3 lemons? you get no fruit symbols? you get 3 bells (the jackpot)? you get no bells? e) you get at least one bar (automatically lose)? .027 .125 .001 .729 .784

5) Suppose the police operate a sobriety checkpoint after 9 p. m 5) Suppose the police operate a sobriety checkpoint after 9 p.m. on a Saturday night when national traffic experts suspect about 12% of drivers have been drinking. Trained officers can correctly decide if a person has been drinking 80% of the time. What’s the probability that any given driver will be detained for drunk driving? a driver who was detained has actually been drinking? c) a driver who was released had actually been drinking? .272 P(incorrectly detains sober) or P(correctly detains drunk) = .2(.88) + .8(.12) P(drunk|detained) = .8(.12)/.272 P(drunk|not detained) = .2(.12)/.728 .353 .033