Notice: On March 31, it was **announced** that Statalist is moving from an email list to a **forum**. The old list will shut down on April 23, and its replacement, **statalist.org** is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From |
Yuval Arbel <yuval.arbel@gmail.com> |

To |
statalist <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: How do I demonstrate that a sample is randomly drawn from a population? |

Date |
Sun, 14 Apr 2013 21:40:53 -0700 |

Nick and David, thank you very much for your very good advises. The idea to weight the sample based on the population sounds great!!! On Sun, Apr 14, 2013 at 4:56 PM, David Hoaglin <dchoaglin@gmail.com> wrote: > Dear Yuval, > > The only conclusive way of showing that a sample is a random sample > from a given population is to demonstrate that the method of selection > produces random samples. > > The students who filled in a questionnaire via the net selected > themselves into the sample, so the details of the mechanism are > unknown. Thus, those students are not a random sample. > > They might be an adequate approximation to a random sample. A common > approach in such situations is to examine all the relevant > characteristics in the population and determine how closely the joint > distribution of those characteristics in the sample resembles the > joint distribution in the population. That will require a much > greater effort than comparing the mean of the sample and the mean of > the population. You can start with the distribution of each > characteristic and move on to each pair of characteristics and then > each combination of three characteristics, and so on. > > If some characteristics of the sample differ from those of the > population, it may be acceptable to reweight the sample, so that the > weighted distributions match those of the population. This process is > used in surveys, where it is known as poststratification (though > usually the sampling mechanism is of better quality). > > David Hoaglin > > On Sun, Apr 14, 2013 at 3:00 PM, Yuval Arbel <yuval.arbel@gmail.com> wrote: >> Dear statalisters, >> >> I have two files: >> >> 1) The first file contains the grades of all population of Open >> University students. >> >> 2) The second file contains the grades of Open University students, >> who filled a questionnaire via the net. >> >> I would like to show that the second file is a random sample drawn >> from the first file. >> >> The question is can I provide a statistical evidence that the sample >> is indeed random? what are the appropriate commands in stata? >> >> P.S. I thought to run the test of difference of means between two >> populations. Having reconsidered, however, I'm not talking here about >> two populations, but rather a sample,which is drawn from a given >> population. >> >> As always, your answers will be very much appreciated >> >> -- >> Dr. Yuval Arbel >> School of Business >> Carmel Academic Center >> 4 Shaar Palmer Street, >> Haifa 33031, Israel >> e-mail1: yuval.arbel@carmel.ac.il >> e-mail2: yuval.arbel@gmail.com > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ -- Dr. Yuval Arbel School of Business Carmel Academic Center 4 Shaar Palmer Street, Haifa 33031, Israel e-mail1: yuval.arbel@carmel.ac.il e-mail2: yuval.arbel@gmail.com * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: How do I demonstrate that a sample is randomly drawn from a population?***From:*David Hoaglin <dchoaglin@gmail.com>

**References**:**st: How do I demonstrate that a sample is randomly drawn from a population?***From:*Yuval Arbel <yuval.arbel@gmail.com>

**Re: st: How do I demonstrate that a sample is randomly drawn from a population?***From:*David Hoaglin <dchoaglin@gmail.com>

- Prev by Date:
**st: Calculating what week of the year a day is** - Next by Date:
**Re: st: SVY medians and Elixhauser** - Previous by thread:
**Re: st: How do I demonstrate that a sample is randomly drawn from a population?** - Next by thread:
**Re: st: How do I demonstrate that a sample is randomly drawn from a population?** - Index(es):