# Project #3600 - Statistics 25 Questions

Question 1 of 25 1.0 Points
A sample of 20 observations has a standard deviation of 4. The sum of the squared deviations from the sample mean is:

A. 288

B. 304

C. 320

D. 400

Question 2 of 25 1.0 Points
If two events are mutually exclusive, what is the probability that both occur at the same time?

A. Cannot be determined from the information given.

B. 0.50

C. 0.00

D. 1.00

Question 3 of 25 1.0 Points
If A and B are any two events with P(A) = .8 and P(B|A) = .4, then the joint probability of A and B is

A. 1.20

B. 0.80

C. 0.40

D. 0.32

Question 4 of 25 1.0 Points
The following data were obtained from a survey of college students. The variable X represents the number of non-assigned books read during the past six months.

x 0 1 2 3 4 5
P (X=x) 0.20 0.25 0.20 0.15 0.10 0.10

Find P(1 < X < 5)

A. 0.45

B. 0.20

C. 0.70

D. 0.30

Question 5 of 25 1.0 Points
The following data were obtained from a survey of college students. The variable X represents the number of non-assigned books read during the past six months.
x 0 1 2 3 4 5
P (X=x) 0.20 0.25 0.20 0.15 0.10 0.10

What is the expected value of X?

A. 3.65

B. 2.0

C. 1.20

D. 6.25

Question 6 of 25 1.0 Points
Which term is NOT synonymous with the expected value of a discrete probability distribution?

A. μ

B. variance

C. theoretical average

D. mean

Question 7 of 25 1.0 Points
The standard normal distribution has a mean of ___ and standard deviation of ___, respectively.

A. 0 and 1

B. 1 and 0

C. 1 and 1

D. 0 and 0

Question 8 of 25 1.0 Points
The continuous distribution characterized by a symmetric, bell-shaped curve is the:

A. exponential distribution

B. Poisson distribution

C. binomial distribution

D. normal distribution

Question 9 of 25 1.0 Points
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. 0.0968

B. 0.0300

C. 0.8364

D. 0.0668

Question 10 of 25 1.0 Points
The average height of flowering cherry trees in a nursery is 11 feet. If the heights are normally distributed with a standard deviation of 1.6, find the probability that a randomly selected cherry tree in this nursery is less than 13 feet tall.

A.  0.67

B. 0.89

C. 0.95

D. 0.11

Question 11 of 25 1.0 Points
If the value of the standard normal random variable Z is positive, then the original score is where in relationship to the mean?

A. to the left of the mean

B. to the right of the mean

C. equal to the mean

D. one standard deviation higher than the mean

Question 12 of 25 1.0 Points
The normal distribution is:

A. the single most important distribution in statistics

B. a density function of a discrete random variable

C. a binomial distribution with only one parameter

D. a discrete distribution

Question 13 of 25 1.0 Points

The following data represent the number of children in a sample of 10 families from Chicago: 4, 2, 1, 1, 5, 3, 0, 1, 0, and 2.

Compute the mean number of children. Place your answer, rounded to two decimal places, in the blank. For example, 3.45 would be a legitimate entry.  _______

Question 14 of 25 1.0 Points

In February 2002 the Argentine peso lost 70% of its value compared to the United States dollar. This devaluation drastically raised the price of imported products. According to a survey conducted by AC Nielsen in April 2002, 68% of the consumers in Argentina were buying fewer products than before the devaluation, 24% were buying the same number of products, and 8% were buying more products. Furthermore, in a trend toward purchasing less-expensive brands, 88% indicated that they had changed the brands they purchased. Suppose the following complete set of results were reported. Use the following data to answer this question.

Number of Products Purchased
Brands Purchased Fewer Same More Total
Same 10 14 24 48
Changed 262 82 8 352
Total 272 96 32 400

Given that a consumer changed brands, what then is the probability that the consumer purchased fewer products than before? Place your answer, rounded to 4 decimal places, in the blank.  ________

Question 15 of 25 1.0 Points

Find the mean of the following probability distribution.
X 1 2 3 4 5
P(X) 0.20 0.10 0.35 0.05 0.30

Round your answer to two decimal place as necessary. For example, 4.56 would be a legitimate entry.

Mean =_______

Question 16 of 25 1.0 Points

An urn contains 12 balls identical in every respect except their color. There are 3 red balls, 7 green balls, and 2 blue balls. You draw two balls from the urn, but replace the first ball before drawing the second. Find the probability that the first ball drawn is red and the second ball drawn is green. Place your answer, rounded to 4 decimal places, in the blank. For example, 0.4567 would be a legitimate entry.  ________

Question 17 of 25 1.0 Points

An ice cream vendor sells three flavors: chocolate, strawberry, and vanilla. Forty five percent of the sales are chocolate, while 30% are strawberry, with the rest vanilla flavored. Sales are by the cone or the cup. The percentages of cones sales for chocolate, strawberry, and vanilla, are 75%, 60%, and 40%, respectively. For a randomly selected sale, define the following events:

= chocolate chosen
= strawberry chosen
= vanilla chosen
= ice cream on a cone
ice cream in a cup

Find the probability that the ice cream was sold on a cone and was chocolate flavor.  Place your answer, rounded to 4 decimal places, in the blank.  For exampe, 0.3456 would be a legitimate entry.   _________

Question 18 of 25 1.0 Points

Suppose that the average weekly earnings for employees in general automotive repair shops is \$450, and that the standard deviation for the weekly earnings for such employees is \$50. A sample of 100 such employees is selected at random.

Find probability that the mean of the sample is less than \$445. Place your answer, rounded to 4 decimal places, in the blank. For example, 0.2345 would be a legitimate entry.  _______

Question 19 of 25 1.0 Points

Mrs. Smith's reading class can read a mean of 175 words per minute with a standard deviation of 20 words per minute. The top 3% of the class is to receive a special award. Assuming that the distribution of words read per minute are normally distributed, what is the minimum number of words per minute a student would have to read in order to get the award? Place your answer, rounded to the nearest whole number, in the blank.   When entering your answer do not use any labels or symbols. Simply provide the numerical value. For example, 123 would be a legitimate entry.

Question 20 of 25 1.0 Points

Scores on a mathematics examination appear to follow a normal distribution with mean of 65 and standard deviation of 15. The instructor wishes to give a grade of “C” to students scoring between the 60th and 70th percentiles on the exam.

What score represents the 60th percentile score on the mathematics exam? Place your answer in the blank, rounded to a whole number. For example, 62 would be a legitimate entry.

Question 21 of 25 1.0 Points

Suppose that the average weekly earnings for employees in general automotive repair shops is \$450, and that the standard deviation for the weekly earnings for such employees is \$50. A sample of 100 such employees is selected at random.

Find the mean the sampling distribution of the average weekly earnings in the sample. Place your answer in the blank. Do not include a dollar sign. For example, 123 would be a legitimate entry.

Question 22 of 25 1.0 Points

A set of final exam scores in an organic chemistry course was found to be normally distributed, with a mean of 73 and a standard deviation of 8.

What is the probability of getting a score of 68 or less on this exam? Place your answer, rounded to 4 decimal places in the blank. For example, 0.3456 would be a legitimate entry.

Question 23 of 25 1.0 Points

A set of final exam scores in an organic chemistry course was found to be normally distributed, with a mean of 73 and a standard deviation of 8.

What is the probability of getting a score higher than 71 on this exam? Place your answer, rounded to 4 decimal places in the blank. For example, 0.3456 would be a legitimate entry.

Question 24 of 25 1.0 Points
If Z is a standard normal variable, then P(Z > 1.50) = 0.9332

True

False

Question 25 of 25 1.0 Points
If Z is a standard normal variable, then P(Z = 1) = 0.3413.

True

False

 Subject Mathematics Due By (Pacific Time) 03/25/2013 08:30 pm
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