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Agresti & Franklin - Statistics (Homework)

James Finch

Statistics, Fall 2010

Instructor: Dr. Friendly

Current Score: 19/27

Due: Tuesday, October 19, 2010 23:00 EDT

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Question
Points
1 2 3 4 5 6 7
1/2 4 6/9 3 4 1 0/4
Total
19/27

Description

Here are some textbook questions from Statistics: The Art and Science of Learning from Data 1/e by Alan Agresti and Christine Franklin published by Prentice Hall. 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. 1/2 points All Submissions Notes Question: AFStat1 1.E.026.
Question part
Points
Submissions
1 2
0/1 1
3/50 1/50
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1/2
 
Your school wants to make an inference about the percentage of students at the school who prefer having a several-day period between the end of classes and the start of final exams to help reduce the level of stress as students prepare for exams. A survey is taken of 100 students.
(a) Identify the sample and the population.
    

Your answer is incorrect.



(b) For the study, explain the purpose of using (i) descriptive statistics, (ii) inferential statistics.


2. 4/4 points All Submissions Notes Question: AFStat1 2.E.010.
Question part
Points
Submissions
1 2 3 4
1 1 1 1
1/50 1/50 1/50 5/50
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4/4
 
The bar chart (using MINITAB) is from a study investigating the factors that influence alligators' choice of food. For 219 alligators captured in four Florida lakes, researchers classified the primary food choice (in volume) found in the alligator's stomach in one of the categories - fish, invertebrate (snails, insects, crayfish), reptile (turtles, baby alligators), bird, or other (amphibian, mammal, plants).
(a) Is primary food choice categorical or quantitative?
    

Your answer is correct.



(b) What is the mode for primary food choice?
    

Your answer is correct.



(c) About what percentage of alligators had fish as the primary food choice?
    

Your answer is correct.



(d) This type of bar chart, with categories listed in order of frequency, has a special name. What is it?
    

Your answer is correct.



3. 6/9 points All Submissions Notes Question: AFStat1 2.E.102.
Question part
Points
Submissions
1 2 3 4 5 6 7 8 9
1 1 1 1 1 0/1 1 0/1 0/1
1/50 1/50 1/50 1/50 1/50 0/50 1/50 0/50 0/50
Total
6/9
 
The data values below represent the prices per share of the 10 most actively traded stocks from the New York Stock Exchange (rounded to the nearest dollar) on Oct. 1, 2003.
3 6 10 12 13 14 30 30 36 49
(a) Construct a stem-and-leaf plot. (Use ascending order. Use NONE for stems with no values.)
StemsLeaves
0
Answer is not case sensitive.
Your answer is correct.
1
Answer is not case sensitive.
Your answer is correct.
2
Answer is not case sensitive.
Your answer is correct.
3
Answer is not case sensitive.
Your answer is correct.
4
Answer is not case sensitive.
Your answer is correct.

(b) Find the median, the first quartile, and the third quartile.
Q1$
Enter a number.
median$
Enter a number.
Your answer is correct.
Q3$
Enter a number.

(c) Sketch a box plot. (Do this on paper. Your instructor may ask you to turn this in.) What feature of the distribution displayed in the plot in (a) is not obvious in the box plot? (Hint: Are there any gaps in the data?)


4. 3/3 points All Submissions Notes Question: AFStat1 3.E.033.
Question part
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Submissions
1 2 3
1 1 1
4/50 1/50 1/50
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3/3
 
In an introductory statistics course, x = midterm exam score and y = final exam score. Both have mean 84 and standard deviation 8. The correlation between the exam scores is 0.75.
(a) Find the regression equation.
=
Enter a number.
Your answer is correct.		 +
Enter a number.
Your answer is correct.x

(b) Find the predicted final exam score for a student with midterm exam score = 86.
=
Enter a number.
Your answer is correct.


5. 4/4 points All Submissions Notes Question: AFStat1 5.E.031.
Question part
Points
Submissions
1 2 3 4
1 1 1 1
1/50 1/50 1/50 3/50
Total
4/4
 
The table below is from a study classifying auto accidents by survival status (S = survived, D = died) and seat belt status of the individual involved in the accident.
Outcome of auto accident by whether subject wore seat belt
Wore Seat BeltSurvived (S)Died (D)Total
Yes (Y)412,994488413,482
No (N)162,9871581164,568
Total575,9812069578,050
(a) Estimate the probability that the individual died (D) in the auto accident.
P(D) =
Enter a number.
Your answer is correct.

(b) Estimate the probability that the individual died, given that they wore a seat belt.
P(D | wore seat belt) =
Enter a number.
Your answer is correct.

Estimate the probability that the individual died, given that they did not wear a seat belt.
P(D | didn't wear seat belt) =
Enter a number.
Your answer is correct.

(c) Are the events of dying and wearing a seat belt independent? Justify your answer.
    

Your answer is correct.



6. 1/1 points All Submissions Notes Question: AFStat1 6.E.013.
Question part
Points
Submissions
1
1
1/50
Total
1/1
 
For the normal distribution shown below, find the probability that an observation falls in the shaded region.
Probability =
Enter a number.
Your answer is correct.


7. –/4 points Notes Question: AFStat1 9.E.026.
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
 
A study of bulimia among college women studied the connection between childhood sexual abuse and a measure of family cohesion (the higher the score, the greater the cohesion). The sample mean on the family cohesion scale was 1.8 for 502 sexually abused students (s = 2.2) and 5.0 for 401 non-abused students (s = 3.0). Assuming equal population standard deviations answer the following questions.
(a) Find the standard error for comparing the means.
SE =
Enter a number.


(b) Construct a 95% confidence interval for the difference between the mean family cohesion for sexually abused students and non-abused students.
(
Enter a number.
 ,
Enter a number.
 )

Interpret.
    


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