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From |
Maarten buis <[email protected]> |

To |
[email protected] |

Subject |
Re: st: store means as a new variable |

Date |
Sat, 23 Feb 2008 14:08:33 +0000 (GMT) |

--- Wencke <[email protected]> wrote: > how can I store estimates of mean values as well as their standard > deviation as new variables in my dataset? > > This is the command for the mean-values, I am using: > mean maxgrip, over(gender ph013_) Given your choice of words I am assuming you do not want the standard deviation of maxgrip but the standard error of the mean. The standard deviation is a measure of the degree in which observations differ to one another with respect to maxgrip, the standard error of the mean is a measure of how precise the estimate of the mean is. There are various ways of doing what you ask. Which one is best depends on what you want to do with it. First notice that -mean- is an estimation command so all tricks discussed in (Newson 2003) and (Buis 2007) are available to you. You can also create a variable containing the mean using -egen-. The -egenmore- package, downloadable from -ssc- also contains a function for creating a variable containing the standard error. To download -egenmore- type -ssc instal egenmore-. The example below illustrates all three methods. *------------- begin example --------------- set more off sysuse auto, clear sort rep78 mean mpg, over(rep78) // discussed in (Buis 2007) mata: b = st_matrix("e(b)")' V = st_matrix("e(V)") se = diagonal(cholesky(diag(V))) b, se end by rep78: egen m = mean(mpg) by rep78: egen se = semean(mpg) list rep78 m se // discussed in (Newson 2003) parmest, norestore list *---------- end example --------------- (For more on how to use examples I sent to the Statalist, see http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html ) Hope this helps, Maarten Buis, Maarten L. (2007), "Stata tip 54: Where did my p-values go?", The Stata Journal, 7(4), pp.584-586. (A pre-publication draft can be downloaded from http://home.fsw.vu.nl/m.buis/wp/pvalue.html ) Newson R. (2003) "Confidence intervals and p-values for delivery to the end user." The Stata Journal, 3(3), pp. 245-269. (A pre-publication draft can be downloaded from http://www.imperial.ac.uk/nhli/r.newson/papers.htm ) ----------------------------------------- Maarten L. Buis Department of Social Research Methodology Vrije Universiteit Amsterdam Boelelaan 1081 1081 HV Amsterdam The Netherlands visiting address: Buitenveldertselaan 3 (Metropolitan), room Z434 +31 20 5986715 http://home.fsw.vu.nl/m.buis/ ----------------------------------------- ___________________________________________________________ Yahoo! Answers - Got a question? Someone out there knows the answer. Try it now. http://uk.answers.yahoo.com/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: store means as a new variable***From:*Wencke <[email protected]>

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