Discrete and Continuous Random Variables

Which of the following random variables should be considered continuous?

• The time it takes for a randomly chosen woman to run 100 meters.

• The number of brothers a randomly chosen person has.

• The number of cars owned by a randomly chosen adult male.

• The number of orders received by a mail-order company in a randomly chosen week.

• None of the above.

• 1/6

• 1/3

• 1/2

• 2/3

• 5/6

Tags

CCSS.7.SP.C.7B

Flip a coin four times. If Z = the number of heads in four flips, then the probability distribution of Z is given in the table. The probability of no more than three tails is

• 0.2500

• 0.3125

• 0.6875

• 0.9375

• None of these

Tags

CCSS.HSS.MD.A.3

CCSS.HSS.MD.A.4

In a certain population of students, the number of calculators a student owns is a random variable X described by the following probability distribution (table).

Which of the following is the mean of X?

• 0.33

• 0.50

• 0.90

• 1.00

• Cannot be computed from given information

Tags

CCSS.6.SP.B.5C

In a certain population of students, the number of calculators a student owns is a random variable X described by the following probability distribution (table).

Which of the following is the standard deviation of X?

• 0.816

• 0.700

• 0.141

• 0.125

• Cannot be computed from given information

The weights of grapefruits of a certain variety are approximately Normally distributed with a mean of 1 pound and a standard deviation of 0.12 pounds.

Which of the following is closest to the probability that a randomly-selected grapefruit weights more than 1.25 pounds?

• 0.0186

• 0.0156

• 0.3156

• 0.4013

• 0.5987

Tags

CCSS.HSS.ID.A.4

Which of the following random variables should be considered NOT discrete?

• The number of sisters your mother has.

• The number of baseball cards your brother owns.

• The time it takes for the average teenager to get ready in the morning.

• The number of hurdles jumped successfully in 100m.

• None of the above.

In a certain population of students, the number of calculators a student owns is a random variable X described by the following probability distribution (table).

Which of the following is the mean of X?

• 0.317

• 0.33

• 1.9

• 2

• Cannot be computed from given information

Tags

CCSS.HSS.MD.A.2

In a certain population of students, the number of calculators a student owns is a random variable X described by the following probability distribution (table).

Which of the following is the standard deviation of X?

• 0.816

• 0.7

• 0.134

• 0.125

• Cannot be computed from given information

The weights of grapefruits of a certain variety are approximately Normally distributed with a mean of 1 pound and a standard deviation of 0.12 pounds.

Which of the following is closest to the probability that a randomly-selected grapefruit weights less than 1.25 pounds?

• 0.0186

• 0.0156

• 0.1056

• 0.8944

• 0.9814

Tags

CCSS.HSS.ID.A.4