Intro Stats
4th Edition
ISBN: 9780321825278
Author: Richard D. De Veaux, Paul F. Velleman, David E. Bock
Publisher: PEARSON
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Textbook Question
Chapter 17, Problem 21E
Dowsing In a rural area, only about 30% of the wells that are drilled find adequate water at a depth of 100 feet or less. A local man claims to be able to find water by “dowsing”—using a forked stick to indicate where the well should be drilled. You check with 80 of his customers and find that 27 have wells less than 100 feet deep. What do you conclude about his claim?
- a) Write appropriate hypotheses.
- b) Check the necessary assumptions and conditions.
- c) Perform the mechanics of the test. What is the P-value?
- d) Explain carefully what the P-value means in context.
- e) What’s your conclusion?
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(c) Because logistic regression predicts probabilities of outcomes, observations used to build a logistic regression model need not be independent.
A. false: all observations must be independent
B. true
C. false: only observations with the same outcome need to be independent
I ANSWERED: A. false: all observations must be independent.
(This was marked wrong but I have no idea why. Isn't this a basic assumption of logistic regression)
Business discuss
Spam filters are built on principles similar to those used in logistic regression. We fit a probability that each message is spam or not spam. We have several variables for each email. Here are a few: to_multiple=1 if there are multiple recipients, winner=1 if the word 'winner' appears in the subject line, format=1 if the email is poorly formatted, re_subj=1 if "re" appears in the subject line. A logistic model was fit to a dataset with the following output:
Estimate
SE
Z
Pr(>|Z|)
(Intercept)
-0.8161
0.086
-9.4895
0
to_multiple
-2.5651
0.3052
-8.4047
0
winner
1.5801
0.3156
5.0067
0
format
-0.1528
0.1136
-1.3451
0.1786
re_subj
-2.8401
0.363
-7.824
0
(a) Write down the model using the coefficients from the model fit.log_odds(spam) = -0.8161 + -2.5651 + to_multiple + 1.5801 winner + -0.1528 format + -2.8401 re_subj(b) Suppose we have an observation where to_multiple=0, winner=1, format=0, and re_subj=0. What is the predicted probability that this message is spam?…
Chapter 17 Solutions
Intro Stats
Ch. 17.2 - A research team wants to know if aspirin helps to...Ch. 17.2 - An allergy drug has been tested and found to give...Ch. 17.2 - The new drug is tested and the P-value is 0.0001....Ch. 17.4 - Prob. 4JCCh. 17.4 - Prob. 5JCCh. 17.4 - Prob. 6JCCh. 17 - Prob. 1ECh. 17 - Prob. 2ECh. 17 - Prob. 3ECh. 17 - Prob. 4E
Ch. 17 - SECTION 15.3 7. Hispanic origin According to the...Ch. 17 - Empty houses According to the 2010 Census, 11.4%...Ch. 17 - Prob. 7ECh. 17 - Prob. 8ECh. 17 - Prob. 9ECh. 17 - Prob. 10ECh. 17 - CHAPTER EXERCISES 15. Hypotheses Write the null...Ch. 17 - More hypotheses Write the null and alternative...Ch. 17 - Negatives After the political ad campaign...Ch. 17 - Dice The seller of a loaded die claims that it...Ch. 17 - Prob. 15ECh. 17 - Cars A survey investigating whether the proportion...Ch. 17 - Prob. 17ECh. 17 - Prob. 18ECh. 17 - Prob. 19ECh. 17 - Prob. 20ECh. 17 - Dowsing In a rural area, only about 30% of the...Ch. 17 - Abnormalities In the 1980s, it was generally...Ch. 17 - Prob. 23ECh. 17 - Educated mothers The National Center for Education...Ch. 17 - 25. Contributions, please, part II In Exercise 23...Ch. 17 - 26. Take the offer, part II In Exercise 24 of...Ch. 17 - 27. Law school 2007 According to the Law School...Ch. 17 - Prob. 28ECh. 17 - Prob. 29ECh. 17 - Scratch and dent An appliance manufacturer...Ch. 17 - Prob. 31ECh. 17 - Prob. 32ECh. 17 - WebZine A magazine is considering the launch of an...Ch. 17 - Seeds A garden center wants to store leftover...Ch. 17 - Prob. 35ECh. 17 - Prob. 36ECh. 17 - Prob. 37ECh. 17 - Acid rain A study of the effects of acid rain on...Ch. 17 - Prob. 39ECh. 17 - TV ads A start-up company is about to market a new...Ch. 17 - Prob. 41ECh. 17 - Prob. 42E
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