Probability with Random Variables

This data is normally distributed. What percent of the data is in the shaded region?

• 68%

• 32%

• 16%

• 50%

A z-score of 2.34 is given for a value. How to find P(X > 2.34)?

• normalcdf(-10000, 2.34, 0, 1)

• normalcdf(2.34, 10000, 0, 1)

• invNorm(2.34, 0, 1)

How to find the z-score with 20% of observations falling ABOVE it in the calculator (ie, to the right):

• invNorm(0.20, 0, 1)

• invNorm(0.80, 0, 1)

• normalcdf(-10000, 0.2, 0, 1)

• normalcdf(0.2, 10000, 0, 1)

Given the probability model in the table below, what is the expected value of the random variable?
  X        50          20        5
P(X)     0.1         0.3      0.6

• 14

• 4.67

• 5

• 7.5

A small store keeps track of the number X of customers that make a purchase during the first hour that the store is open each day. Based on the records, X has the following probability distribution. What is the average number of customers that the owner can expect to make a purchase in the first hour of opening?

• 0.2

• 1.4

• 2.0

• 3.0

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

Is the data given valid?

• Yes, all the probabilities add up to 1

• No, All the probabilities do not add up to 1

• Yes, the data does not go on forever

• No, The data goes on forever

A coin is tossed and then a regular 6-sided die is rolled. What is the probability of the resulting outcome being

(tails, even)?

• 1/2

• 1/12

• 1/6

• 1/4

• 0

• .86

• .70

• 1

What is the P( not purple) on this spinner?

• 2/5

• 1/5

• 4/5

• 3/5