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Need to modify & finish: Test Review??

Last updated over 1 year ago

6 questions

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Question 1

1.

Illegal music downloading has become a big problem: 29% of Internet users download music files, and 67% of downloaders say they don’t care if the music is copyrighted.
Find the probability that a randomly selected Internet user downloads music and doesn’t care if it’s copyrighted.
Keep your answer as a decimal to four places.

Question 2

2.

A statistics class with 30 students has 10 males and 20 females. Choose 2 of the students in the class at random.
Find the probability that both are female.
P(2 female)=P(1st is a female)*P(2nd is a female | 1st is a female)
Remember - the # will change after the first is chosen.

Keep your answer as a decimal, round to four places.

Question 3

3.

Using the information from #2:
Find the probability that one of the students is female and the other is male.

Hint: order does not matter, this is P(F & M)= P(F)P(M|F first) + P(M)P(F|M first)
Enter your answer as a decimal, round to four places past the decimal.

Question 4

4.

In a recent month, 88% of automobile drivers filled their vehicles with regular gasoline, 2% purchased midgrade gas, and 10% bought premium gas. Of those who bought regular gas, 28% paid with a credit card. Of customers who bought midgrade and premium gas, 34% and 42%, respectively, paid with a credit card. Suppose we select a customer at random.
Draw a tree diagram to model this chance process on a scratch sheet of paper.
Find the probability that the customer paid with a credit card.
Enter your answer as a decimal rounded to four places.

Question 5

5.

Use the information from #4:
Given that the customer paid with a credit card, find the probability that she or he bought premium gas.

Question 6

6.

A string of Christmas lights contains 20 lights. The lights are wired in series, so that if any light fails, the whole string will go dark.
Each light has probability 0.98 of working for a 3-year period. The lights fail independently of each other. Find the probability that the string of lights will remain bright for 3 years.
Hint: how many lights are in a string?
P(3 strings lit)=