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From | Maarten buis <maartenbuis@yahoo.co.uk> |
To | statalist@hsphsun2.harvard.edu |
Subject | RE: RE: st: A bug in egen and gen? |
Date | Sat, 19 Feb 2011 17:59:41 +0000 (GMT) |
--- On Sat, 19/2/11, Liao, Junlin wrote: > For two, case in mind, Stata store 4.1 not as > 4.1, but as many digits of 9's following 4.0. What information is stored in the number 4.1. Since you said 4.1 and not 4.10 or 4.100, we know that this is some number between 4.05 and 4.15. It obviously makes no sense to try to store such a number with 16 digits of accuracy. We only have information on the first two, storing it as a double is not going to magically give us information on the remaining 14 digits. If information just isn't there, and you will not create it by storing it as a double. When storing data you need to remember where data comes from, and data collection is necesarily a messy process. Two digits of accuaracy seems to me about right (or even optimistic) for most measurements. Imagine a survey: the interviewer needs to ask the question correctly (they often do not), than the respondent needs to understant the question (they often do not), than the respondents needs to know the answer (they often do not), than the interviewer needs to understand the answer, and it needs to fit it in the answer form (often this is a problem), than the data needs to be typed in correctly (ever heard of typos...). It is a miracle we get any useful information out of a survey at al! There is no chance that we will get anything with an accuracy of 16 digits out of that... -- Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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/