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From |
Maarten buis <maartenbuis@yahoo.co.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: error bars |

Date |
Mon, 16 Jun 2008 13:05:25 +0100 (BST) |

--- moleps islon <moleps2@gmail.com> wrote: > I need to make a an error-bar graph categorised by year. I've tried > using serrbar mean(x) etc, but I cant find a command for the standard > error. Do I need to run a CI, generate a new variable from the ci > result and feed that into serrbar? There are many ways of doing this. For instance you can use methods discussed in (Buis 2007) (a convenient estimatation command would in this case be -mean-), or you can remember that the standard error of the mean is the standard deviation divided by the square root of the number of observations, like in the example below: *-------------- begin example ----------------------- sysuse nlsw88, clear gen mis = missing(wage, age) bys age: egen mwage = mean(wage) bys age: egen sdwage = sd(wage) bys age mis: gen se = sdwage/sqrt(_N) if mis == 0 serrbar mwage se age, scale(1.96) *-------------- end example ------------------------- Notice that a fixed scale is slightly problematic here as idealy this scale should depend on the number of observations (a t-test), but 1.96 should work fine in large samples. For a more flexible approach, where you can take all this into account see: (Newson 2003) -- maarten M.L. Buis (2007), "Stata tip 54: Where did my p-values go?", The Stata Journal, 7(4), pp.584--586. http://home.fsw.vu.nl/m.buis/wp/pvalue.html R. Newson (2003), "Confidence intervals and p–values for delivery to the end user", The Stata Journal, 3(3), pp. 245--269. http://www.stata-journal.com/article.html?article=st0043 ----------------------------------------- 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/ ----------------------------------------- __________________________________________________________ Sent from Yahoo! Mail. A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html * * 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/

**Follow-Ups**:**RE: st: error bars***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**References**:**st: error bars***From:*"moleps islon" <moleps2@gmail.com>

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