Question 1

The total area of a normal probability distribution is

Accepted Answer

A)  between -3.0 and 3.0. 
B)  1.00. 
C)  dependent on a value of 'z'. 
D)  approximated by the binomial distribution.

Question 2

i. Asymptotic means that the normal curve gets closer and closer to the X-axis but never actually touches it.
Ii) When referring to the normal probability function, there is not just one of them; there is a "family" of them.
Iii) Some normal probability distributions have equal arithmetic means, but their standard deviations may be different.

Accepted Answer

A)  (i), (ii) and (iii) are all correct statements 
B)  (i) is a correct statement but not (ii) or (iii). 
C)  (i) and, (iii) are correct statements but not (ii). 
D)  (ii) and, (iii) are correct statements but not (i). 
E)  All statements are false

Question 3

A financial advising company has determined that the price-to-earnings ratios for 20 randomly selected publicly traded companies range between 0.9 and 2.9. Given that the price-to-earnings ratios are uniformly distributed, what percent of price-to-earnings ratios are between 1.90 and 2.48?

Accepted Answer

A)  19% 
B)  20% 
C)  26% 
D)  29% 
E)  None of the choices are correct

Question 4

The mean amount of gasoline and services charged by Key Refining Company credit customers is $70 per month. The distribution of amounts spent is approximately normal with a standard deviation of
$10) What is the probability of selecting a credit card customer at random and finding the customer charged between $70 and $83?

Accepted Answer

A)  0.1962 
B)  0.4032 
C)  0.3413 
D)  0.4750 
E)  None of the choices are correct

Question 5

Replacement times for TV sets are normally distributed with a mean of 8.2 years and a standard deviation of 1.1 years, (based on data from "Getting Things Fixed," Consumer Reports).

-If you want to provide a warranty so that only 3% of the TV sets will be replaced before the warranty expires, the length of warranty you would recommend would be _____years.

Accepted Answer

The answer of Replacement times for TV sets are normally...

Question 6

A sample of 500 evening students revealed that their annual incomes were normally distributed with a mean income of $50,000 and a standard deviation of $4,000. How many students earned between $45,000 and $53,000?

Accepted Answer

A)  170 
B)  273 
C)  334 
D)  387 
E)  None of the choices are correct

Question 7

i. A z-score is the distance between a selected value (X) and the population mean (μ) divided by the population standard deviation (σ).
Ii) The standard normal distribution is a special normal distribution with a mean of 0 and a standard deviation of 1.
Iii) A computed z for X values to the right of the mean is negative.

Accepted Answer

A)  (i), (ii) and (iii) are all correct statements 
B)  (i) is a correct statement but not (ii) or (iii). 
C)  (i) and, (iii) are correct statements but not (ii). 
D)  (i) and, (ii) are correct statements but not (iii). 
E)  All statements are false

Question 8

The mean score of a college entrance test is 500; the standard deviation is 75. The scores are normally distributed. What percent of the students scored below 320?

Accepted Answer

A)  About 50.82% 
B)  About 34.13% 
C)  About 7.86% 
D)  About 0.82% 
E)  None of the choices are correct

Question 9

Ball-Bearings, Inc. produces ball bearings automatically on a Kronar BBX machine. For one of the ball bearings, the mean diameter is set at 20.00 mm (millimetres). The standard deviation of the production over a long period of time was computed to be 0.150 mm. What percent of the ball bearings will have diameters 20.27 mm or more?

Accepted Answer

A)  41.00% 
B)  12.62% 
C)  3.59% 
D)  85.00% 
E)  None of the choices are correct

Exam 6: The Normal Probability Distribution

The total area of a normal probability distribution is

A financial advising company has determined that the price-to-earnings ratios for 20 randomly selected publicly traded companies range between 0.9 and 2.9. Given that the price-to-earnings ratios are uniformly distributed, what percent of price-to-earnings ratios are between 1.90 and 2.48?

A sample of 500 evening students revealed that their annual incomes were normally distributed with a mean income of $50,000 and a standard deviation of $4,000. How many students earned between $45,000 and $53,000?

The mean score of a college entrance test is 500; the standard deviation is 75. The scores are normally distributed. What percent of the students scored below 320?