Chapter 7
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 490 and 560?
0.2823
The duration of a red light at a particular intersection in a city is uniformly distribution from one to four minutes. What is the probability that you will wait at the particular red light between 2.5 and 3 minutes?
1/6
Which of the following statements are true about the symmetric characteristic of the normal probability distribution? Select all that apply.
16%
Suppose that customer usage time of computers in the public library is uniformly distributed with a minimum of 20 minutes and a maximum of 80 minutes. What is the standard deviation of the distribution?
17.3
The time it takes a wholesaler to fill an order follows a uniform distribution from three to six days What is the probability that they will fill an order between day 3 and 5?
2/3
What do we mean when we say there is a "family" of normal distributions? Choose two of these statements.
A single equation describes all normal distributions. Distributions may have different means and standard deviations but still be "normal" in shape.
Which statements below accurately characterize a uniform distribution. Select all that apply.
Areas within the distribution represent probabilities. The area inside the rectangle (i.e the frequency polygon) must be one.
Which of the following is true regarding continuous and discrete random variables.
Continuous random variables usually result from measuring.
How would you describe the shape of the Normal Distribution?
It is "bell" shaped, and symmetrical with the center at μ.
Which statements describe the mean of a Uniform Distribution. Select all that apply.
It is always equal to the median. It is always in the middle of the minimum and maximum values.
Where does the curve of the normal distribution touch the x-axis?
It never touches, but approaches asymptotically in both directions.
What are the upper and lower limits of the random variable for the Normal distribution?
No limits. It is asymptotic in both directions.
Since the normal probability distribution is symmetrical about the mean, which of the following is true?
The area on each side of the mean is 0.5.
Which of the following statements are true with respect to both the Standard Normal distribution and any normal probability distribution? Choose all that apply.
The areas are equal to 1. A normal probability distribution can be converted into a standard normal distribution.
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 The random variable is always positive. It is characterized by only one parameter, known as the "rate" parameter.
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.
The distribution with μ = 20 is to the right of the other distribution. The distribution with σ = 2 is more peaked.
Which of the following statements are true of the Standard Normal Distribution?
The mean (μ) is zero. The standard deviation (σ) is 1
Which one of the following is a result of the normal probability distribution being bell-shaped?
The mean median and mode are at the center
For a uniform distribution, the probability is defined as P(x) = 1b−a1b-a. What do the symbols b and a represent?
The min and max values
Which of the following statements are true about the symmetric characteristic of the normal probability distribution? Select all that apply.
The shape to the left of the mean is a mirror image of the shape to the right of the mean. The area on each side of the mean equals one-half.
Which of the following is an example of a continuous random variable?
The square footage of a house.
The area under a uniform distribution (or any probability distribution) represents a probability. Which one of the following statements characterizes this area?
The total area is one
What kind of events are described by an Exponential distribution?
Times between events in a sequence.
The minimum and maximum values of the random variable are sufficient to describe which of these distributions?
Uniform
Which one of the following is true about the uniform distribution?
Which one of the following is true about the uniform distribution?
A z value is a distance from the
mean
The average score on an IQ test is 110 and the standard deviation is 10. What is the z-value for a score of 130?
z=2
A Uniform distribution has a minimum value for the random variable of "a" and a maximum of "b". What is the formula for the mean?
μ = a+b/2
