Discrete Probability Distributions

Is this a valid probability distribution?

• No

• Yes

Is this a valid probability distribution?

• No

• Yes

The table represents the probability of guessing correct on a 5 question true-false quiz. Find the mean and the standard deviation. Round answers to the nearest tenth.

• μ = .4; σ = 7.5

• μ = 2.5; σ = 1.1

• μ = 3; σ = 1.3

• μ = .1; σ = 0

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

• 2.80

• 2.93

• 0.10

• 0.14

The table above shows the number of cell phones per household in a small town. Find the standard deviation. Round to the nearest hundredth.

• 0.80

• 1.70

• 1.31

• 1.00

• Yes, because all of the probabilities are between 0 and 1 inclusive and the sum of all the probabilities is 1.

• No, all probabilities are not be between 0 and 1 inclusive.

• No, because the sum of all the probabilities is not 1.

• Yes, because the distribution is symmetric

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

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