From: Dimitris Rizopoulos <dimitris.rizopoulos_at_med.kuleuven.be>

Date: Fri 22 Sep 2006 - 11:17:22 GMT

Dimitris Rizopoulos

Ph.D. Student

Biostatistical Centre

School of Public Health

Catholic University of Leuven

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Fri Sep 22 21:21:11 2006

Date: Fri 22 Sep 2006 - 11:17:22 GMT

try the following:

B <- 10000

index <- rowSums(matrix(rbinom(B*2, 1, 0.5), ncol = 2))
sum(index == 2) / sum(index > 0)

I hope it helps.

Best,

Dimitris

Dimitris Rizopoulos

Ph.D. Student

Biostatistical Centre

School of Public Health

Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium

Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm

- Original Message ----- From: "Jacob van Wyk" <jlvw@na.rau.ac.za> To: <r-help@stat.math.ethz.ch> Sent: Friday, September 22, 2006 12:57 PM Subject: [R] A simple resampling problem

> Dear UseRs

*>
**> I would like to show my students how to use "resampling" to solve
**> the
**> following simple problem:
**>
**> If a family has two children of which one is a boy, what is the
**> probability that the other child is also a boy.
**> The answer is (obviously) 1/3, and can be show easily using the
**> usual
**> methods.
**> But I would like to get the students to think of resampling, by
**> doing
**> the following:
**> Flip two coins repeatedly, denoted 0 and 1 (1 for boy, say). Discard
**> those pairs that both contain 0.
**>>From those left over, count how many pairs are (1,1).
**> Divide this number by the number available to choose from (i.e. all
**> pairs, except (0,0)).
**> This will then give 1/3 (more or less of course).
**>
**> Can somebody help me to code this efficiently, or elegantly (and
**> smartly) in R, without loops etc.
**> It is intended for first year students that are only starting to
**> learn
**> about statistics (or probability theory), and R of course.
**>
**> Thank you for your time.
**> Regards
**> Jacob
**>
**>
**>
**>
**> Jacob L van Wyk
**> Department of Statistics
**> University of Johannesburg, APK
**> P O Box 524
**> Auckland Park 2006
**> South Africa
**> Tel: +27 11 489 3080
**> Fax: +27 11 489 2832
**>
**>
**>
**> [[alternative HTML version deleted]]
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide
**> http://www.R-project.org/posting-guide.html
**> and provide commented, minimal, self-contained, reproducible code.
**>
*

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Fri Sep 22 21:21:11 2006

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