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- 1. Multiple ChoiceIf P(A) = 0.20, P(B|A)=0.60 and P(B|A')=0.25, then P(A|B) =0.37500.70590.62500.2941
- 2. Multiple ChoiceA virus has infected 1.8% of a population. A test detects this virus 95% of the time when it is actually present, but it returns a false positive 3% of the time when the virus is not present.
If a person selected at random from this population tests positive for the virus, what is the probability that this person is actually infected? [Round to the nearest percent.]37%63%34%66% - 3. Multiple ChoiceA witness claims that a black car was involved in a nighttime accident. Police know that, at night, witnesses identify black cars correctly 90% of the time, but 30% of the time misidentify cars of other colors as black.
If 8% of cars in the city are black, what is the probability that a black car really was involved in the accident?0.20690.08450.79310.6200 - 4. Multiple ChoiceA rare species of dragonfly is always born with an extra set of wings. However, common dragonflies also sometimes get an extra set of wings through a mutation. 0.3% of dragonflies in a certain habitat belong to this rare species, and the extra-wing mutation is known to occur in 0.1% of common dragonflies.
You see a dragonfly in this habitat with an extra pair of wings. What is the probability that it is a member of the rare species?0.75060.10030.00040.9996 - 5. Multiple Choice83% of a certain airline's flights depart on time. Of these flights, 90% also arrive on time. 30% of flights from this airline that depart late manage to make up time in the air to still arrive on time.
You see a flight from this airline arriving on time. What is the probability that it departed on time?0.93610.96080.97210.8532 - 6. Multiple ChoiceA test returns a positive result for a virus 90% of the time when the virus actually is present. However, it also returns a positive result 8% of the time when the virus is not present.
0.1% of people in a certain population are infected with this virus. Is this test an effective way to search for this virus? Why or why not?Yes, 90% of people with the virus test positive.No, almost 99% of people with positive results do not have the virus.No, 8% of people without the virus test positive.Yes, 92% of people without the virus test negative. - 7. Multiple ChoiceUrn A contains three white and five black balls. Urn B contains two white and eight black balls.
I hand you one of these urns at random and you select a ball from that urn at random.
If that ball is white, what is the probability that I handed you Urn A? [Round to the nearest percent.]60%65%55%70% - 8. Multiple Choice
In a town, it was found that 90% of drivers wore seat belts. On 60% of occasions, if a driver was not wearing a seat belt they would be fined for speeding. But, if they were wearing a seat belt, they would be fined for speeding 20% of the time. Find the probability that a driver who was fined for speeding was wearing a seat belt?
5/8
1/2
3/4
40%
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