Analyze Discrete Random Variables

A marketing survey compiled data on the number of cars in households.  If X = the number of cars in a randomly selected household, and we omit the rare cases of more than 5 cars, then X has the following probability distribution: 
X           0          1          2          3           4           5    
P(X)   0.24    0.37    0.20    0.11    0.05     0.03
What is the probability that a randomly chosen household has at least two cars?

• 0.20
• 0.29
• 0.39
• 0.61

The table represents the probability of guessing correct on a 5 question true-false quiz.  Find the probability for at least 4 questions correct.

• .03125
• .15625
• .3125
• .1875

The table above shows the number of cell phones per household in a small town. Find the mean give your answer to the nearest hundredth.

• 2.80

• 2.93

• 0.10

• 0.14

A stockbroker estimates that at the end of the year, there is a 40% chance a stock will be worth £50, a 35% chance it will be worth £60 and a 25% chance it will be worth £70. What expected value does this broker assign to this stock's end-of-the-year price?

• £58.50

• £60.00

• £62.50

• £65.00

In a certain community, 30% of households have 1 child, 43% have 2 children, and 27% have 3 children. If a household is selected at random, what is the expected number of children in that household? HINT: A Probability table may be helpful.

• 2.00
• 2.13
• 1.97
• 1.27

A discrete random variable X has the probability distributions shown in the table. Find the value of k.

• 1/3

• 7/12

• 1/12

• 1/4

Determine which of the following distribution is NOT a probability distribution.

• A

• B

• C

• D

Is this a probability distribution?

• No, the sum of p(x) does not equal 1.

• Yes, all p(x) are between 0 and 1.

• No, all p(x) are not between 0 and 1.

• Yes, the sum p(x) is 1.

The table above shows a television station's advertisement sales. The distribution of sales for one 24-hour day is given. Calculate E(X). Round to the nearest hundredth.

• 31.8

• 15.68

• 0.20

• 1.00

The table above shows a television station's advertisement sales. The distribution of sales for one 24-hour day is given. Calculate the standard deviation. Round to the nearest hundredth.

• 35.76

• 268.1

• 16.3

• 1279.35