Question 1

Given that Z is a standard normal variable, the value z for which P(Z   z) = 0.2580 is:

Accepted Answer

A)  0.70 
B)  0.758 
C)  -0.65 
D)  0.242 
E)  -0.242 
A)  0.70 
B)  0.758 
C)  -0.65 
D)  0.242 
E)  -0.242

Question 2

A student government representative claims that 55% of the student body of a local university favor a move to Division I in college football. A random sample of 2000 students is selected.
What is the expected number of students that will favor the move to Division I?
______________
What is the approximate probability that less than 1150 students of the 2000 selected will favor the move to Division I?
______________

Accepted Answer

The answer of A student government representative claims that 55%...

Question 3

Given that Z is a standard normal random variable, P(-1.0   Z   1.5) is:

Accepted Answer

A)  0.7745 
B)  0.8413 
C)  0.0919 
D)  0.9332 
E)  1.932 
A)  0.7745 
B)  0.8413 
C)  0.0919 
D)  0.9332 
E)  1.932

Question 4

In general, the binomial probability P(X   x) is approximated by the area under the normal curve to the right of x - .5.

Accepted Answer

A) True 
 B)False

Question 5

Many different types of continuous random variables give rise to a large variety of probability density functions, including:

Accepted Answer

A)  the binomial probability distribution 
B)  the hypergeometric probability distribution 
C)  the normal probability distribution 
D)  the Poisson probability distribution 
E)  both the binomial probability distribution and the hypergeometric probability distribution 
A)  the binomial probability distribution 
B)  the hypergeometric probability distribution 
C)  the normal probability distribution 
D)  the Poisson probability distribution 
E)  both the binomial probability distribution and the hypergeometric probability distribution

Question 6

Given a normal random variable x with mean   and standard deviation   , the variance of the standard normal random variable z associated with x is 0.

Accepted Answer

A) True 
 B)False

Question 7

A car dealership has found that the length of time before a major repair is required on the new cars it sells is normally distributed, with a mean equal of 36 months and a standard deviation of 9 months. If the dealer wants only 5% of the cars to fail before the end of the guarantee period, for how many months should the cars be guaranteed?
______________

Accepted Answer

The answer of A car dealership has found that the...

Question 8

Using the standard normal curve, the area between z = -1.50 and z = 1.50 is 0.4332.

Accepted Answer

A) True 
 B)False

Question 9

The z-score representing the first quartile of the standard normal distribution is:

Accepted Answer

A)  0.67 
B)  -0.67 
C)  1.28 
D)  -1.28 
E)  0.28 
A)  0.67 
B)  -0.67 
C)  1.28 
D)  -1.28 
E)  0.28

Question 10

A random variable x is normally distributed with m = 100 and   = 20.
What is the median of this distribution?
______________
Find   .
______________
Find   .
______________

Accepted Answer

The answer of A random variable x is normally distributed...

Question 11

Given that Z is a standard normal random variable, the area to the left of a value z is expressed as:

Accepted Answer

A)  P(Z ≥ z) 
B)  P(Z ≤ z) 
C)  P(0 ≤ Z ≤ z) 
D)  P(Z ≥ -z) 
E)  P(z ≤ Z ≤ 0) 
A)  P(Z ≥ z) 
B)  P(Z ≤ z) 
C)  P(0 ≤ Z ≤ z) 
D)  P(Z ≥ -z) 
E)  P(z ≤ Z ≤ 0)

Question 12

The normal random variable's density function is (1) single-peaked above the variable's mean, median, and mode, all of which are equal to one another, (2) perfectly symmetric about this peaked central value and, thus, bell-shaped, and (3) characterized by tails extending indefinitely in both directions from the center, approaching (but never touching) the horizontal axis, which implies a positive probability for finding values of the random variable anywhere between minus infinity and plus infinity.

Accepted Answer

A) True 
 B)False

Question 13

Let   be a z-score that is unknown but identifiable by position and area. If the symmetrical area between -   and +   is 0.9544, the value of   is 2.0.

Accepted Answer

A) True 
 B)False

Question 14

One difference between a binomial random variable x and a standard normal random variable z is that with the binomial random variable we cannot determine P(x = a), while for the standard normal variable we can determine P(z = a).

Accepted Answer

A) True 
 B)False

Question 15

Which of the following is not a characteristic of the normal distribution?

Accepted Answer

A)  It is symmetric. 
B)  It has a bell-shape. 
C)  Mean = median = mode. 
D)  All of these. 
E)  None of these. 
A)  It is symmetric. 
B)  It has a bell-shape. 
C)  Mean = median = mode. 
D)  All of these. 
E)  None of these.

Question 16

For a continuous random variable, P(x   a) = P(x > a) because P(x = a) = 0.

Accepted Answer

A) True 
 B)False

Question 17

If x is a normal random variable with mean   = 4 and standard deviation   = 2, and Y is a normal random variable with mean   = 10 and standard deviation   = 5, then P(x < 0) = P(Y < 0).

Accepted Answer

A) True 
 B)False

Question 18

A chemical manufacturer sells its product in steel drums. The net weight of the chemical in the drums has a normal distribution with mean 310 pounds and standard deviation 4 pounds. The manufacturer guarantees its customers each drum will contain at least 300 pounds of the chemical.
What percentage of the drums will satisfy this guarantee?
______________

Accepted Answer

The answer of A chemical manufacturer sells its product in...

Question 19

Using the standard normal curve, the z-score representing the 90th percentile is 1.28.

Accepted Answer

A) True 
 B)False

Question 20

Twenty-five psychology instructors have formed a committee to pick next year's textbook, and they have narrowed their decision down to two equally good books, one with a better bibliography and references, and the other with a better format and illustrations. Since the books are considered to be equally good, we will assume the probability an instructor chooses either book is 0.5 and the instructors' decisions are made independently.
Using the binomial distribution, find the probability 15 or more instructors choose the book with the better format and illustrations.
______________
Use the normal approximation to the binomial to find the probability 15 or more instructors choose the book with the better format and illustrations.
______________
Compare the results in parts (a) and (b). Is the normal approximation a good approximation?
______________

Accepted Answer

The answer of Twenty-five psychology instructors have formed a committee...

Given that Z is a standard normal variable, the value z for which P(Z z) = 0.2580 is:

Given that Z is a standard normal random variable, P(-1.0 Z 1.5) is:

In general, the binomial probability P(X x) is approximated by the area under the normal curve to the right of x - .5.

Many different types of continuous random variables give rise to a large variety of probability density functions, including:

Given a normal random variable x with mean and standard deviation , the variance of the standard normal random variable z associated with x is 0.

Using the standard normal curve, the area between z = -1.50 and z = 1.50 is 0.4332.

The z-score representing the first quartile of the standard normal distribution is:

A random variable x is normally distributed with m = 100 and = 20. What is the median of this distribution? Find . Find . __

Given that Z is a standard normal random variable, the area to the left of a value z is expressed as:

Let be a z-score that is unknown but identifiable by position and area. If the symmetrical area between - and + is 0.9544, the value of is 2.0.

One difference between a binomial random variable x and a standard normal random variable z is that with the binomial random variable we cannot determine P(x = a), while for the standard normal variable we can determine P(z = a).

Which of the following is not a characteristic of the normal distribution?

For a continuous random variable, P(x a) = P(x > a) because P(x = a) = 0.

If x is a normal random variable with mean = 4 and standard deviation = 2, and Y is a normal random variable with mean = 10 and standard deviation = 5, then P(x < 0) = P(Y < 0).

Using the standard normal curve, the z-score representing the 90th percentile is 1.28.

Describing Data With Graphs

Describing Data With Numerical Measures

Describing Bivariate Data

Probability and Probability Distributions

Several Useful Discrete Distributions

Sampling Distributions

Large-Sample Estimation

Large-Sample Tests of Hypotheses

Inference From Small Samples

The Analysis of Variance

Linear Regression and Correlation

Multiple Regression Analysis

Analysis of Categorical Data

Nonparametric Statistics

Filters

Exam 6: The Normal Probability Distribution

Given that Z is a standard normal variable, the value z for which P(Z z) = 0.2580 is:

Given that Z is a standard normal random variable, P(-1.0 Z 1.5) is:

In general, the binomial probability P(X x) is approximated by the area under the normal curve to the right of x - .5.

Many different types of continuous random variables give rise to a large variety of probability density functions, including:

Given a normal random variable x with mean and standard deviation , the variance of the standard normal random variable z associated with x is 0.

Using the standard normal curve, the area between z = -1.50 and z = 1.50 is 0.4332.

The z-score representing the first quartile of the standard normal distribution is:

A random variable x is normally distributed with m = 100 and = 20. What is the median of this distribution? ______________ Find . ______________ Find . ______________

Given that Z is a standard normal random variable, the area to the left of a value z is expressed as:

Let be a z-score that is unknown but identifiable by position and area. If the symmetrical area between - and + is 0.9544, the value of is 2.0.

One difference between a binomial random variable x and a standard normal random variable z is that with the binomial random variable we cannot determine P(x = a), while for the standard normal variable we can determine P(z = a).

Which of the following is not a characteristic of the normal distribution?

For a continuous random variable, P(x a) = P(x > a) because P(x = a) = 0.

If x is a normal random variable with mean = 4 and standard deviation = 2, and Y is a normal random variable with mean = 10 and standard deviation = 5, then P(x < 0) = P(Y < 0).

Using the standard normal curve, the z-score representing the 90th percentile is 1.28.

Describing Data With Graphs

Describing Data With Numerical Measures

Describing Bivariate Data

Probability and Probability Distributions

Several Useful Discrete Distributions

Sampling Distributions

Large-Sample Estimation

Large-Sample Tests of Hypotheses

Inference From Small Samples

The Analysis of Variance

Linear Regression and Correlation

Multiple Regression Analysis

Analysis of Categorical Data

Nonparametric Statistics

Filters

A random variable x is normally distributed with m = 100 and = 20. What is the median of this distribution? Find . Find . __