Question 1

For a normal curve, if the mean is 25 minutes and the standard deviation is 5 minutes, the area to the right of 25 minutes is 0.50.

Accepted Answer

A) True 
 B)False

Question 2

The publisher of a daily newspaper claims that 90% of its subscribers are under the age of 30. Suppose that a sample of 300 subscribers is selected at random. Assuming the claim is correct, approximate the probability of finding at least 240 subscribers in the sample under the age of 30.

Accepted Answer

The answer of The publisher of a daily newspaper claims...

Question 3

If Z is a standard normal random variable, the area between z = 0.0 and z =1.30 is 0.4032, while the area between z = 0.0 and z = 1.50 is 0.4332. What is the area between z = -1.30 and z = 1.50? $\begin{array}{|l|l|}
\hline \text { A. } & 0.0300 \
\hline \text { B. } & 0.0668 \
\hline \text { C. } & 0.0968 \
\hline \text { D. } & 0.8364 \
\hline
\end{array}$

Accepted Answer

The answer of If Z is a standard normal random...

Question 4

Given a binomial distribution with n trials and probability p of a success on any trial, a conventional rule of thumb is that the normal distribution will provide an adequate approximation of the binomial distribution if: $\begin{array}{|l|l|}
\hline  A&n p \geq 5 \text { and } n(1-p) \geq 5 \
\hline  B&n p \leq 5 \text { and } n(1-p) \leq 5\
\hline  C&n p \geq 5 \text { and } n(1-p) \leq 5\
\hline  D&n p \leq 5 \text { and } n(1-p) \geq 5\
\hline 
\end{array}$

Accepted Answer

The answer of Given a binomial distribution with n trials...

Question 5

A certain brand of flood lamps has a lifetime that is normally distributed with a mean of 3750 hours and a standard deviation of 300 hours.
a. What proportion of these lamps will last for more than 4000 hours?
b. What lifetime should the manufacturer advertise for these lamps in order that only 2% of the lamps will burn out before the advertised lifetime?

Accepted Answer

The answer of A certain brand of flood lamps has...

Question 6

A smaller standard deviation of a normal distribution indicates that the distribution becomes: $\begin{array}{|l|l|}
\hline  A&\text { more skewed to the left.}\
\hline  B&\text {flatter and wider. }\
\hline  C&\text { narrower and more peaked.}\
\hline  D&\text { symmetrical.}\
\hline 
\end{array}$

Accepted Answer

The answer of A smaller standard deviation of a normal...

Question 7

Given that z is a standard normal random variable, a negative value of z indicates that the standard deviation of z is negative.

Accepted Answer

A) True 
 B)False

Question 8

If the mean of an exponential distribution is 4, then the value of the parameter $\lambda$ is: $\begin{array}{|l|l|}
\hline\text { A. } & 4 . \
\hline \text { B. } & 0.25 . \
\hline \text { C. } & 2 . \
\hline \text { D. } & 0.5 . \
\hline
\end{array}$

Accepted Answer

The answer of If the mean of an exponential distribution...

Question 9

Given that the random variable X is normally distributed with a mean of 20 and a standard deviation of 7, P(28 $\le$ X $\le$30) is: $\begin{array}{|l|l|}
\hline \text { A. } & 2 \
\hline \text { B. } & 0.0507 . \
\hline \text { C. } & 0.8729 \
\hline \text { D. } & 0.9236 \
\hline
\end{array}$

Accepted Answer

The answer of Given that the random variable X is...

Question 10

The active lifetime of laptop computers is normally distributed, with a mean of 36 months and a standard deviation of 6 months.
a. What is the probability that a randomly selected laptop will last less than 3.5 years?
b. What proportion of the laptops will last more than 32 months?
c. What proportion of the laptops will last between 2 and 4 years?

Accepted Answer

a. 0.8413.

Question 11

The recent average starting salary for new college graduates in computer information systems is $47 500. Assume that salaries are normally distributed, with a standard deviation of $4500.
a. What is the probability of a new graduate receiving a salary between $45 000 and $50 000?
b. What is the probability of a new graduate getting a starting salary in excess of $55 000?
c. What percentage of starting salaries are no more than $42 250?
d. What is the cut-off for the bottom 5% of the salaries?
e. What is the cut-off for the top 3% of the salaries?

Accepted Answer

a. 0.4246.
b. 0.0475

Question 12

Using the standard normal curve, the probability or area between z = -1.28 and z = 1.28 is 0.1003

Accepted Answer

A) True 
 B)False

Question 13

Given that X is a binomial random variable, the binomial probability P(X $\geq$ x) is approximated by the area under a normal curve to the right of: $\begin{array}{|l|l|}
\hline\text { A. } & x-0.5 \
\hline \text { B. } & x+0.5 \
\hline \text { C. } & x-1 . \
\hline \text { D. } & x+1 . \
\hline
\end{array}$

Accepted Answer

The answer of Given that X is a binomial random...

Question 14

The probability density function f(x) for a uniform random variable X defined over the interval [1, 11] is: $\begin{array}{|l|l|}
\hline\text { A. } & \text { any value between } 1 \text { and } 11 . \
\hline \text { B. } & 0.100 . \
\hline \text { C. } & 0.091 \
\hline \text { D. } & \text { above } 11 . \
\hline
\end{array}$

Accepted Answer

The answer of The probability density function f(x) for a...

Question 15

Find the following probabilities:
a. P(X $\leq$ 1).
b. P(X $\geq$ 2).
c. P(1 $\leq$ X $\leq$ 2).
d. P(X = 3).

Accepted Answer

a. 0.4375.

Question 16

A standard normal distribution is a normal distribution with: $\begin{array}{|l|l|}
\hline  A&\text { a mean of zero and a standard deviation of one.}\
\hline  B&\text {a mean of one and a standard deviation of zero. }\
\hline  C&\text { a mean usually larger than the standard deviation}\
\hline  D&\text { a mean always larger than the standard deviation.}\
\hline 
\end{array}$

Accepted Answer

The answer of A standard normal distribution is a normal...

Question 17

The probability density function f(x) of a random variable X that is normally distributed is completely determined once the: $\begin{array}{|l|l|}
\hline  A&\text { mean and median of $ X $ are specified}\
\hline  B&\text { median and mode of $ X $ are specified}\
\hline  C&\text {mean and mode of $ X $ are specified.}\
\hline  D&\text {mean and variance of $ X $ are specified. }\
\hline 
\end{array}$

Accepted Answer

The answer of The probability density function f(x) of a...

Question 18

Given that Z is a standard normal random variable, P(-1.23 $\le$ Z $\le$1.89) is: $\begin{array}{|l|l|}
\hline\text { A. } & 0.1903 . \
\hline \text { B. } & 0.9706 . \
\hline \text { C. } & 0.8907 . \
\hline \text { D. } & 0.7803 . \
\hline
\end{array}$

Accepted Answer

The answer of Given that Z is a standard normal...

Question 19

If the random variable X is uniformly distributed between 40 and 60, then P(35 $\le$X $\le$45) is: $\begin{array}{|l|l|}
\hline\text { A. } & 1.0 . \
\hline \text { B. } & 0.5 . \
\hline \text { C. } & 0.25 \
\hline \text { D. } & 0.0 . \
\hline
\end{array}$

Accepted Answer

The answer of If the random variable X is uniformly...

Question 20

Researchers studying the effects of a new diet found that the weight loss over a one-month period by those on the diet was normally distributed with a mean of 7 kg and a standard deviation of 2.5 kg.
a. What proportion of the dieters lost more than 10 kg?
b. What proportion of the dieters gained weight?
c. If a dieter is selected at random, what is the probability that the dieter lost at most 5 kg?

Accepted Answer

a. 0.1151.

For a normal curve, if the mean is 25 minutes and the standard deviation is 5 minutes, the area to the right of 25 minutes is 0.50.

The publisher of a daily newspaper claims that 90% of its subscribers are under the age of 30. Suppose that a sample of 300 subscribers is selected at random. Assuming the claim is correct, approximate the probability of finding at least 240 subscribers in the sample under the age of 30.

If Z is a standard normal random variable, the area between z = 0.0 and z =1.30 is 0.4032, while the area between z = 0.0 and z = 1.50 is 0.4332. What is the area between z = -1.30 and z = 1.50? A. 0.0300 B. 0.0668 C. 0.0968 D. 0.8364

A smaller standard deviation of a normal distribution indicates that the distribution becomes: A more skewed to the left. B flatter and wider. C narrower and more peaked. D symmetrical.

Given that z is a standard normal random variable, a negative value of z indicates that the standard deviation of z is negative.

If the mean of an exponential distribution is 4, then the value of the parameter $\lambda$ is: A. 4. B. 0.25. C. 2. D. 0.5.

Given that the random variable X is normally distributed with a mean of 20 and a standard deviation of 7, P(28 $\le$ X $\le$ 30) is: A. 2 B. 0.0507. C. 0.8729 D. 0.9236

Using the standard normal curve, the probability or area between z = -1.28 and z = 1.28 is 0.1003

Given that X is a binomial random variable, the binomial probability P(X $\geq$ x) is approximated by the area under a normal curve to the right of: A. x-0.5 B. x+0.5 C. x-1. D. x+1.

The probability density function f(x) for a uniform random variable X defined over the interval [1, 11] is: A. any value between 1 and 11. B. 0.100. C. 0.091 D. above 11.

Find the following probabilities: a. P(X $\leq$ 1). b. P(X $\geq$ 2). c. P(1 $\leq$ X $\leq$ 2). d. P(X = 3).

A standard normal distribution is a normal distribution with: A a mean of zero and a standard deviation of one. B a mean of one and a standard deviation of zero. C a mean usually larger than the standard deviation D a mean always larger than the standard deviation.

The probability density function f(x) of a random variable X that is normally distributed is completely determined once the: A mean and median of X are specified B median and mode of X are specified C mean and mode of X are specified. D mean and variance of X are specified.

Given that Z is a standard normal random variable, P(-1.23 $\le$ Z $\le$ 1.89) is: A. 0.1903. B. 0.9706. C. 0.8907. D. 0.7803.

If the random variable X is uniformly distributed between 40 and 60, then P(35 $\le$ X $\le$ 45) is: A. 1.0. B. 0.5. C. 0.25 D. 0.0.

What Is Statistics

Types of Data, Data Collection and Sampling

Graphical Descriptive Methods Nominal Data

Graphical Descriptive Techniques Numerical Data

Numerical Descriptive Measures

Probability

Random Variables and Discrete Probability Distributions

Statistical Inference: Introduction

Sampling Distributions

Estimation: Describing a Single Population

Estimation: Comparing Two Populations

Hypothesis Testing: Describing a Single Population

Hypothesis Testing: Comparing Two Populations

Inference About Population Variances

Analysis of Variance

Additional Tests for Nominal Data: Chi-Squared Tests

Simple Linear Regression and Correlation

Multiple Regression

Model Building

Nonparametric Techniques

Statistical Inference: Conclusion

Time-Series Analysis and Forecasting

Index Numbers

Decision Analysis

Filters

Exam 8: Continuous Probability Distributions

For a normal curve, if the mean is 25 minutes and the standard deviation is 5 minutes, the area to the right of 25 minutes is 0.50.

The publisher of a daily newspaper claims that 90% of its subscribers are under the age of 30. Suppose that a sample of 300 subscribers is selected at random. Assuming the claim is correct, approximate the probability of finding at least 240 subscribers in the sample under the age of 30.

If Z is a standard normal random variable, the area between z = 0.0 and z =1.30 is 0.4032, while the area between z = 0.0 and z = 1.50 is 0.4332. What is the area between z = -1.30 and z = 1.50? A. 0.0300 B. 0.0668 C. 0.0968 D. 0.8364

A smaller standard deviation of a normal distribution indicates that the distribution becomes: A more skewed to the left. B flatter and wider. C narrower and more peaked. D symmetrical.

Given that z is a standard normal random variable, a negative value of z indicates that the standard deviation of z is negative.

If the mean of an exponential distribution is 4, then the value of the parameter λ\lambdaλ is: A. 4. B. 0.25. C. 2. D. 0.5.

Given that the random variable X is normally distributed with a mean of 20 and a standard deviation of 7, P(28 ≤\le≤ X ≤\le≤ 30) is: A. 2 B. 0.0507. C. 0.8729 D. 0.9236

Using the standard normal curve, the probability or area between z = -1.28 and z = 1.28 is 0.1003

Given that X is a binomial random variable, the binomial probability P(X ≥\geq≥ x) is approximated by the area under a normal curve to the right of: A. x-0.5 B. x+0.5 C. x-1. D. x+1.

The probability density function f(x) for a uniform random variable X defined over the interval [1, 11] is: A. any value between 1 and 11. B. 0.100. C. 0.091 D. above 11.

Find the following probabilities: a. P(X ≤\leq≤ 1). b. P(X ≥\geq≥ 2). c. P(1 ≤\leq≤ X ≤\leq≤ 2). d. P(X = 3).

A standard normal distribution is a normal distribution with: A a mean of zero and a standard deviation of one. B a mean of one and a standard deviation of zero. C a mean usually larger than the standard deviation D a mean always larger than the standard deviation.

The probability density function f(x) of a random variable X that is normally distributed is completely determined once the: A mean and median of X are specified B median and mode of X are specified C mean and mode of X are specified. D mean and variance of X are specified.

Given that Z is a standard normal random variable, P(-1.23 ≤\le≤ Z ≤\le≤ 1.89) is: A. 0.1903. B. 0.9706. C. 0.8907. D. 0.7803.

If the random variable X is uniformly distributed between 40 and 60, then P(35 ≤\le≤ X ≤\le≤ 45) is: A. 1.0. B. 0.5. C. 0.25 D. 0.0.

What Is Statistics

Types of Data, Data Collection and Sampling

Graphical Descriptive Methods Nominal Data

Graphical Descriptive Techniques Numerical Data

Numerical Descriptive Measures

Probability

Random Variables and Discrete Probability Distributions

Statistical Inference: Introduction

Sampling Distributions

Estimation: Describing a Single Population

Estimation: Comparing Two Populations

Hypothesis Testing: Describing a Single Population

Hypothesis Testing: Comparing Two Populations

Inference About Population Variances

Analysis of Variance

Additional Tests for Nominal Data: Chi-Squared Tests

Simple Linear Regression and Correlation

Multiple Regression

Model Building

Nonparametric Techniques

Statistical Inference: Conclusion

Time-Series Analysis and Forecasting

Index Numbers

Decision Analysis

Filters

If the mean of an exponential distribution is 4, then the value of the parameter $\lambda$ is: A. 4. B. 0.25. C. 2. D. 0.5.

Given that the random variable X is normally distributed with a mean of 20 and a standard deviation of 7, P(28 $\le$ X $\le$ 30) is: A. 2 B. 0.0507. C. 0.8729 D. 0.9236

Given that X is a binomial random variable, the binomial probability P(X $\geq$ x) is approximated by the area under a normal curve to the right of: A. x-0.5 B. x+0.5 C. x-1. D. x+1.

Find the following probabilities: a. P(X $\leq$ 1). b. P(X $\geq$ 2). c. P(1 $\leq$ X $\leq$ 2). d. P(X = 3).

Given that Z is a standard normal random variable, P(-1.23 $\le$ Z $\le$ 1.89) is: A. 0.1903. B. 0.9706. C. 0.8907. D. 0.7803.

If the random variable X is uniformly distributed between 40 and 60, then P(35 $\le$ X $\le$ 45) is: A. 1.0. B. 0.5. C. 0.25 D. 0.0.