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| From | Steve Samuels <sjsamuels@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: RE: AW: ratio function |
| Date | Thu, 1 Apr 2010 09:30:10 -0400 |
2010/4/1 Roman Kasal <kasal@trexima.cz>: > > but it ignores unpaired data :( And it should. Data (x,y) (1,2) (2,4) (3,6) (100,.) will give an entirely different view of the data if the unpaired observation is included in a mean or ratio calculation. Or consider data with x missing in half the pairs and y missing in the other half; the ratio of means would be meaningless. The formulas for standard errors for ratios assume that the data are paired. Formally, they are based on the residual MSE of a regression of y on x through the origin. You cannot do that regression with unpaired data. If your concern is missing data, the solution is to impute the missing values before analysis. Steve > > Steven Samuels sjsamuels@gmail.com 18 Cantine's Island Saugerties NY 12477 USA Voice: 845-246-0774 Fax: 206-202-4783 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/