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Devore-Probability&Statistics for Engineering 6/e (Homework)

James Finch

Statistics, Fall 2010

Instructor: Dr. Friendly

Current Score: 0/29

Due: Saturday, October 23, 2010 23:00 EDT

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Question
Points
1 2 3 4 5
0/3 0/12 0/4 0/4 0/6
Total
0/29

Description

Here are some textbook questions from Probability and Statistics for Engineering 6/e by Jay L. Devore published by Brooks/Cole Publishing. Click here for a list of all of the questions coded in WebAssign.


Instructions

This demo assignment allows many submissions and allows you to try another version of the same question for practice.



1. –/3 points Notes Question: DevoreStat6 2.P.022.
Question part
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1 2 3
0/1 0/1 0/1
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0/3
 
The route used by a certain motorist in commuting to work contains two intersections with traffic signals. The probability that he must stop at the first signal is 0.36, the analogous probability for the second signal is 0.54, and the probability that he must stop at at least one of the two signals is 0.71.
(a) What is the probability that he must stop at both signals?
Enter a number.

(b) What is the probability that he must stop at the first signal but not at the second one?
Enter a number.

(c) What is the probability that he must stop at exaclty one signal?
Enter a number.


2. –/12 points Notes Question: DevoreStat6 3.P.023.
Question part
Points
Submissions
1 2 3 4 5 6 7 8 9 10 11 12
0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1
0/50 0/50 0/50 0/50 0/50 0/50 0/50 0/50 0/50 0/50 0/50 0/50
Total
0/12
 
An insurance company offers its policyholders a number of different premium payment options. For a randomly selected policyholder, let X = the number of months between successive payments. The cdf of X is as follows.

F(x)={( 0 text( ) x<1, 0.38 text( ) 1 <= x < 3, 0.51 text( ) 3 <= x < 4, 0.53 text( )4 <= x < 6, 0.9 text( )6 <= x < 12, 1 text( ) 12 <= x)
(a) What is the pmf of X?
x
Enter a number.
Enter a number.
Enter a number.
Enter a number.
Enter a number.
p(x)
Enter a number.
Enter a number.
Enter a number.
Enter a number.
Enter a number.

(b) Using just the cdf, compute P(3 X 6) and P(4 X).
P(3 X 6)
Enter a number.
P(4 X)
Enter a number.


3. –/4 points Notes Question: DevoreStat6 4.P.057.
Question part
Points
Submissions
1 2 3 4
0/1 0/1 0/1 0/1
0/50 0/50 0/50 0/50
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0/4
 
Suppose the time spent by a randomly selected student who uses a desktop connected to a server has a gamma distribution with mean 10.5 min and variance 36.75 min 2.
(a) What are the values of and ?
=
Enter a number.
=
Enter a number.
(b) What is the probability that a student uses the terminal for at most 24 min?
Enter a number.

(c) What is the probability that a student spends between 20 and 40 min using the terminal?
Enter a number.


4. –/4 points Notes Question: DevoreStat6 7.P.014.
Question part
Points
Submissions
1 2 3 4
0/1 0/1 0/1 0/1
0/50 0/50 0/50 0/50
Total
0/4
 
An article gave the following summary information for fracture strengths (MPa) of n = 178 ceramic bars fired in a particular kiln.

= 88.51s = 3.95

(a) Calculate a (two-sided) confidence interval for true average fracture strength using a confidence level of 95%.
(
Enter a number.
,
Enter a number.
)
Does it appear that true average fracture strength has been precisely estimated?
    


(b) Suppose the investigators had believed a priori that the population standard deviation was about 5 MPa. Based on this supposition, how large a sample would have been required to estimate to within .5 MPa with 95% confidence?
Enter a number.


5. –/6 points Notes Question: DevoreStat6 8.P.049.
Question part
Points
Submissions
1 2 3 4 5 6
0/1 0/1 0/1 0/1 0/1 0/1
0/50 0/50 0/50 0/50 0/50 0/50
Total
0/6
 
The paint used to make lines on roads must reflect enough light to be clearly visible at night. Let denote the true average reflectometer reading for a new type of paint under consideration. A test of H0: = 20 versus Ha: 20 will be based on a random sample of size n from a normal population distribution. What conclusion is a appropriate in each of the following situations?
(a) n = 13, t = 3.2, = .05
H0, based on a critical value of
Enter a number.
.
(b) n = 7, t = 1.8, = .01
H0, based on a critical value of
Enter a number.
.
(c) n = 25, t = -0.2, = .05
H0, based on a critical value of
Enter a number.
.
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