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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

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

Subject |
RE: st: Create a normalized variable |

Date |
Thu, 20 Nov 2008 17:56:53 -0000 |

Maarten's warning is well taken. Roughly speaking, my experience is that natural scientists (physicists, biologists, etc.) are more likely to take normalised as meaning scaled to [0, 1], far more commonly by (value - min) / (max - min) than by percentile ranks. The more statistics you know, the more likely you are to regard (value - mean) / sd as a natural standardisation. Nick n.j.cox@durham.ac.uk Maarten buis This very much depends on what you mean with normalized. Sometimes it means a transformation that will result in a variable that is nearer to a normal (Gaussian) distribution. You cannot mean that, as than the resulting variable cannot range between 0 and 1 (as a normal distribution ranges between minus infinity and plus infinity). Sometimes, the term is used for standardization. A common method is to subtract the mean and divide by the standard deviation (the results are sometimes called z-scores). Again you cannot mean that as the resulting variable will not range between 0 and 1. An alternative way to standardize would be to use percentile ranks, which gives for each respondent the proportion of respondents thas smaller, poorer, dumber, etc than that respondent. This will give you a standardized variable wich ranges between 0 and 1. The downside of this approach is that it is less common so you have more to explain, and that it is a non-linear transformation, in particular you only keep information obout the ordering of individuals and loose information about the distances between them. Don't get me wrong though, I like this form of standardization, it is just not suitable for every application (which should not be a big surprise). The way to compute these is discussed here: http://www.stata.com/support/faqs/stat/pcrank.html Finaly, a linear transformation that will lead to a score between 0 and 1 is to simply divide that variable by 8. * * 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/

**Follow-Ups**:**RE: st: Create a normalized variable***From:*Maarten buis <maartenbuis@yahoo.co.uk>

**References**:**st: Create a normalized variable***From:*mmolina@uniroma3.it

**Re: st: Create a normalized variable***From:*Maarten buis <maartenbuis@yahoo.co.uk>

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