Geometric and Binomial Random Variable

A random variable X has a mean of 5 and a st. dev of 0.40. A random variable Y has a mean of 8 and a st. dev of 0.60. If both are independent, what is the st. dev of X - Y?

• 0.52
• 0.72
• 1.0
• Not here

A random variable X has a mean of 5 and a st. dev of 0.40. A random variable Y has a mean of 8 and a st. dev of 0.60. If both are independent, what is the mean of X + Y?

• 13
• 6.5
• 14
• Not here.

Cool TV game show
Players win prizes with probabilities shown:
P($0) = .70
P($500) = .25
P($5,000) = .05
What are the mean and the standard deviation of the prize variable?

• Mu = $375; sigma = $361
• Mu = $375; sigma = $1,083
• Mu = $1,833; sigma = $1,816
• Inadequate info is provided.

Which of the following is NOT an assumption of the Binomial distribution?

• All trials must be independent.
• Each trial must be classified as a success or a failure.
• All trials are dependent on each other.
• The number of successes in the trials is counted.

The variance of the sum of two random variables X and Y is

• σ_X+σ_Y
• (σ_X)²+(σ_Y)²
• σ_X+σ_Y but only if X and Y are independent
• (σ_X)²+(σ_Y)² but only if X and Y are independent

It is known that about 90% of widgets made by Buckley Industries meet specifications. Every hour a sample of 18 widgets is selected at random for testing and the number of widgets that meet specifications is recorded. What is the approximate mean and standard deviation of the number of widgets meeting specifications?

• μ=1.62; σ=1.414
• μ=1.62; σ=1.265
• μ=16.2; σ=1.62
• μ=16.2; σ=1.273

Tags

CCSS.HSS.IC.A.1

CCSS.HSS.ID.A.4

CCSS.HSS.MD.A.2

CCSS.HSS.MD.A.3

The American Red Cross says that about 11% of the U.S. population has Type B blood. A blood drive is being held at your school. How many blood donors should the American Red Cross expect to collect from until it gets a donor with Type B blood? 

• 9.1 donors
• 8.5 donors
• 10.3 donors
• Cannot be determined.

Tags

CCSS.HSS.MD.A.2

CCSS.HSS.MD.A.3

CCSS.HSS.MD.B.5

The American Red Cross says that about 11% of the U.S. population has Type B blood. A blood drive is being held at your school.What is the probability that exactly 2 of the first 20 blood donors have Type B blood? 

• 0.316
• 0.282
• 0.001
• Not here

A set of 20 cards consists of 10 purple cards and 10 green cards.  If you turn cards over one at a time after shuffling them and wait until you get your first purple, what distribution is it

• binomial, n= 20 and p= .5
• geometric p= .5
• none- same probability isn't happening each time
• normal distribution

In order for a random variable x to have a geometric distribution, which of the following must it satisfy

• not independent
• Succcess or failure
• set number of trials
• p>.7

Tags

CCSS.HSS.CP.A.2

CCSS.HSS.CP.A.3