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From |
Sofia Ramiro <sofiaramiro@hotmail.com> |

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

Subject |
RE: st: Age-specific reference intervals (xrigls) - no equation for SD? |

Date |
Wed, 6 Jun 2012 20:54:01 +0100 |

> > Dear Statalist members, > > I sent this question some days ago but did not get any answer, so I send it again. Please let me know if the problem is my question not being clear enough or missing some information. > > I am trying to define age-specific reference intervals with the command xrigls. > > > > However, when running it, for some of the variables for which I want to define the age intervals I get an equation for the mean (with the corresponding power), but no equation for the SD - example below. I don't understand why. Can any of you explain this? > > Are the values derived without the SD equation also right? > > I don't understand why in the 1st table (FP powers) the change appears always as 0. I inspected the data and there is variation in this variable and throughout the different ages. > > > > Thanks > > > > Sofia > > > > > > > > . xrigls schober15 age if sample==1, fp(m:df 4,s:df 2) centile(2.5 10 25 75 90 97.5) detail > > > > --- FP Powers --- > > Cycle Mean SD Deviance Change Residual SS > > ----------------------------------------------------------------- > > 0 1 1217.262 0.000 509.4298 > > 1 1 1217.262 0.000 509.4298 > > 2 1 1217.262 0.000 509.4298 > > > > Final deviance = 1217.262 (393 observations). > > Power(s) for mean curve = 1. > > > > Regression for mean curve > > ------------------------- > > (sum of wgt is 3.4287e+02) > > > > Source | SS df MS Number of obs = 393 > > -------------+------------------------------ F( 1, 391) = 24.05 > > Model | 31.3308787 1 31.3308787 Prob > F = 0.0000 > > Residual | 509.429806 391 1.30288953 R-squared = 0.0579 > > -------------+------------------------------ Adj R-squared = 0.0555 > > Total | 540.760685 392 1.37949154 Root MSE = 1.1414 > > > > ------------------------------------------------------------------------------ > > schober15 | Coef. Std. Err. t P>|t| [95% Conf. Interval] > > -------------+---------------------------------------------------------------- > > age | -.0203814 .0041562 -4.90 0.000 -.0285528 -.01221 > > _cons | 7.191451 .1913316 37.59 0.000 6.815284 7.567619 > > ------------------------------------------------------------------------------ > > > > > > * > > * 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/ > > * > * 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/ * * 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: Age-specific reference intervals (xrigls) - no equation for SD?***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: Age-specific reference intervals (xrigls) - no equation for SD?***From:*Sofia Ramiro <sofiaramiro@hotmail.com>

**st: Age-specific reference intervals (xrigls) - no equation for SD?***From:*Sofia Ramiro <sofiaramiro@hotmail.com>

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