Question 1

The assembly time for a product is uniformly distributed between 6 to 10 minutes.The standard deviation of assembly time (in minutes) is approximately

Accepted Answer

A)  1.3333. 
B)  1.1547. 
C)  0.1111. 
D)  0.5773.

Question 2

What is the mean of x, given the function below? f(x) = (1/10) e-x/10 x  0

Accepted Answer

A)  0.10 
B)  10 
C)  100 
D)  1,000

Question 3

What is the probability that x is between 3 and 6, given the function below? f(x) = (1/10) e-x/10 x  0

Accepted Answer

A)  0.4512 
B)  0.1920 
C)  0.2592 
D)  0.6065

Question 4

The time it takes to travel from home to the office is normally distributed with μ = 25 minutes and σ = 5 minutes.What is the probability the trip takes more than 32 minutes?

Accepted Answer

A)  .9701 
B)  .1995 
C)  .9192 
D)  .0808

Question 5

A normal probability distribution

Accepted Answer

A)  can have mean of any numerical value. 
B)  needs to have a mean of 0. 
C)  has a standard deviation of 0. 
D)  must have a standard deviation of 1 and a mean of 0.

Question 6

The exponential probability distribution is used with

Accepted Answer

A)  a discrete random variable. 
B)  a continuous random variable. 
C)  any probability distribution with an exponential term. 
D)  an approximation of the binomial probability distribution.

Question 7

When a continuous probability distribution is used to approximate a discrete probability distribution, a value of 0.5 is added to and/or subtracted from the

Accepted Answer

A)  area. 
B)  value of x. 
C)  value of z. 
D)  value of µ.

Question 8

For a normal distribution, a negative value of z indicates

Accepted Answer

A)  a mistake has been made in computations, because z is always positive. 
B)  the area corresponding to the z is negative. 
C)  the z is to the left of the mean. 
D)  the z is to the right of the mean.

Question 9

The uniform distribution defined over the interval from 25 to 40 has the probability density function

Accepted Answer

A)  f(x) = 1/40 for all x. 
B)  f(x) = 5/8 for 25 $\lt$x $\lt$40 and f(x) = 0 elsewhere. 
C)  f(x) = 1/25 for 0 < x < 25 and f(x) = 1/40 for 26 $\lt$ x $\lt$ 40. 
D)  f(x) = 1/15 for 25 < x $\lt$ 40 and f(x) = 0 elsewhere.

Question 10

Larger values of the standard deviation result in a normal curve that is

Accepted Answer

A)  skewed to the right. 
B)  skewed to the left. 
C)  narrower and more peaked. 
D)  wider and flatter.

Question 11

x is a normally distributed random variable with a mean of 24 and a standard deviation of 6.The probability that x is less than 11.5 is

Accepted Answer

A)  0.0186. 
B)  0.9814. 
C)  0.0076. 
D)  0.9924.

Question 12

z is a standard normal random variable.The P(-1.5 < z < 1.09) equals

Accepted Answer

A)  0.4322. 
B)  0.3621. 
C)  0.7953. 
D)  0.0711.

Question 13

The highest point of a normal curve occurs at

Accepted Answer

A)  one standard deviation to the right of the mean. 
B)  two standard deviations to the right of the mean. 
C)  approximately three standard deviations to the right of the mean. 
D)  the mean.

Question 14

The starting salaries of individuals with an MBA degree are normally distributed with a mean of $40,000 and a standard deviation of $5,000.What percentage of MBA's will have starting salaries of $34,000 to $46,000?

Accepted Answer

A)  38.49% 
B)  38.59% 
C)  50% 
D)  76.98%

Question 15

Given that z is a standard normal random variable, what is the value of z if the area to the right of z is 0.5?

Accepted Answer

A)  0.0000 
B)  1.0000 
C)  0.1915 
D)  0.3413

Question 16

z is a standard normal random variable.What is the value of z if the area to the right of z is 0.7444?

Accepted Answer

A)  -0.66 
B)  0.66 
C)  -1.66 
D)  1.66

Question 17

The mean of a standard normal probability distribution

Accepted Answer

A)  is always equal to zero. 
B)  can be any value as long as it is positive. 
C)  can be any value. 
D)  is always greater than zero.

Question 18

Given that z is a standard normal random variable, what is the probability that z  -2.12?

Accepted Answer

A)  0.4830 
B)  0.9830 
C)  0.017 
D)  0.966

Question 19

For a normal distribution, a positive value of z indicates that

Accepted Answer

A)  all the observations must have had positive values. 
B)  the area corresponding to the z is either positive or negative. 
C)  the sample mean is smaller than the population mean. 
D)  the sample mean is larger than the population mean.

Question 20

For the standard normal probability distribution, the area to the left of the mean is

Accepted Answer

A)  -0.5. 
B)  0.5. 
C)  any value between 0 to 1. 
D)  1.

Exam 6: Continuous Probability Distributions