Error on p. 446?

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Error on p. 446?

Dave Palmer
First, thanks so much for taking the time to write the book. I'm just getting into it and it's been outstanding thus far.

I'm rusty with this so please forgive me if I'm erring and needlessly taking your time, but in reviewing Appendix A: The Basics of Counting, example A.11 begins, "[i]f the students must answer three questions out of five in section A...". The answer for that portion is listed as 30 possible combinations. In going through that a few handful of times, I believe the correct answer is 10.

Also, while I have you, on page 15 using Excel's CORREL function with the matrix size described and variable integers between 1 and 10, I couldn't get a correlation coefficient >= .5 between any given column and column S. I refreshed about 15-20 times assuming I was doing something incorrectly. Any ideas on that would also be appreciated.

Again, apologies if these are errors on my part. Just trying to work myself through the entirety of the book to ensure I understand.

Best,
Dave
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RE: Error on p. 446?

chesterton

Dave,

Pardon the response from a fellow reader. Looks to me like you’re correct on your first point. I too calculate a value of 10.

But as to your second point, I was able to get correlation coefficients > 0.5 on most attempts, using 20 rows of data columns A through S. Did you perhaps create too many rows? In the book example, there are 20 rows of data. With many more than that, it’s less likely you’ll see columns that correlate with each other.

Greg

 

From: Dave Palmer [via Risk Assessment with Bayesian Networks] [mailto:ml-node+[hidden email]]
Sent: Sunday, January 04, 2015 10:12 PM
To: Chesterton, Gregory
Subject: Error on p. 446?

 

First, thanks so much for taking the time to write the book. I'm just getting into it and it's been outstanding thus far.

I'm rusty with this so please forgive me if I'm erring and needlessly taking your time, but in reviewing Appendix A: The Basics of Counting, example A.11 begins, "[i]f the students must answer three questions out of five in section A...". The answer for that portion is listed as 30 possible combinations. In going through that a few handful of times, I believe the correct answer is 10.

Also, while I have you, on page 15 using Excel's CORREL function with the matrix size described and variable integers between 1 and 10, I couldn't get a correlation coefficient >= .5 between any given column and column S. I refreshed about 15-20 times assuming I was doing something incorrectly. Any ideas on that would also be appreciated.

Again, apologies if these are errors on my part. Just trying to work myself through the entirety of the book to ensure I understand.

Best,
Dave


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RE: Error on p. 446?

norman@eecs.qmul.ac.uk
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Dave and Greg

Yes A.11 shoulkd be 10 not 30. Thanks - I will update the errata page.

And I agree with Greg about the excel example.

Norman Fenton
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RE: Error on p. 446?

Dave Palmer
Greg and Norman,

Thanks so much for the prompt input. I'll take another crack at the coefficients in Excel.

Best,
Dave
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