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From |
Austin Nichols <austinnichols@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: comparing nested models |

Date |
Thu, 3 Feb 2011 11:59:51 -0500 |

Neil Shephard <nshephard@gmail.com> : You would certainly not get a better fit by specifying . reg wage age instead of . reg wage i.age but then one must balance parsimony against parametric assumptions. Note also that you can test your parametric assumptions, but that is related to what the poster was asking: sysuse nlsw88, clear reg wage age i.age test 35.age 36.age 37.age 38.age 39.age 40.age 41.age 42.age 43.age 44.age 45.age reg wage c.age##c.age##c.age test c.age#c.age c.age#c.age#c.age Most would assume log wages are a quadratic or higher order polynomial function of age without much theoretical justification (google "Mincer wage equation" for discussion), but note that age is categorical in every dataset already... Though I suppose it could be measured with millisecond precision as of Stata 10. On Thu, Feb 3, 2011 at 11:36 AM, Neil Shephard <nshephard@gmail.com> wrote: > On Thu, Feb 3, 2011 at 4:09 PM, Nikolas Asasa <lenta2008@yahoo.com> wrote: >> Dear All, >> I have two models aiming to estimate effect of age on wage. In the first model age is recorded in 5 categories. In the second model age is recorded in 10 categories. >> The question is how to compare goodness of fit of two models? >> >> In principle I would apply F-test, but I am not sure whether "test" procedure in Stata allows me to do it? Should I use ANOVA instead? > > If you have the actual age of individuals would you not get the best > fit by simply using all of the information on age and wage... > > wage = a*age + b > > ...under a linear regression? > > There are many, many reasons why you shouldn't classify continuous > variables into categorical. Frank Harrell's page somes many of these > up nicely http://biostat.mc.vanderbilt.edu/wiki/Main/CatContinuous > > Neil * * 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: comparing nested models***From:*Neil Shephard <nshephard@gmail.com>

**References**:**st: comparing nested models***From:*Nikolas Asasa <lenta2008@yahoo.com>

**Re: st: comparing nested models***From:*Neil Shephard <nshephard@gmail.com>

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