Business Statistics Ch. 7

Which of the following statements are true of the Standard Normal Distribution?

The standard deviation (σ) is 1 The mean (μ) is zero.

Scores on a graduate school entrance exam follow a normal distribution with a mean of 560 and a standard deviation of 90. What is the probability that a randomly chosen test taker will score between 560 and 640?

0.3133

On average a certain website receives 3 hits each hour (1 hit each 20 minutes). Use the exponential distribution to find the probability that it will receive a hit in less than 30 minutes.

0.78

On average a customer service call line receives a call every three minutes. Use the exponential distribution to find the probability that the next call will arrive in less than five minutes.

0.81

How does the Standard Normal distribution relate to any normal probability distribution? Choose all that apply,

A normal probability distribution can be converted into a standard normal distribution. The areas are equal to 1.

What percentage of the area under the normal curve is more than 1 standard deviation from the mean?

Approximately 32%

Which of the following is true regarding continuous and discrete random variables.

Continuous random variables usually result from measuring.

Which is the best definition of the z-value?

The distance between a value x and the mean, μ, divided by the standard deviation, σ

Choose the three characteristics from the following list that describe the exponential distribution.

The distribution is asymmetrical and positively skewed It is characterized by only one parameter, known as the "rate" parameter. The random variable is always positive.

Suppose you have two normal distributions: one has μ=16 and σ=2 and the other has μ=20 and σ=3. Which of the following statements are true? Select all that apply.l

The distribution with σ=2 is a more peaked. The distribution with μ=20 is to the right of the other distribution.

Which one of the following items of information is required to fully define a uniform distribution?

The minimum and maximum value of the variable,

Which of the following random experiments could not be described by an exponential distribution?

The probability that five customers will use the bank's ATM in the next hour.

Which of the following is an example of a continuous random variable?

The square footage of a house.

On average a customer service call line handles a rate of three per minute. If we are going to describe this wait time for service using an exponential distribution, what is the rate parameter?

λ = 1/3 of a minute

A uniform distribution has a minimum value for the random variable of "a" and a maximum of "b". What is the formula for the standard deviation of the distribution?

σ = √(b−a)212