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From |
Steve Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: Re: st: RE: AW: ratio function |

Date |
Fri, 23 Apr 2010 10:40:44 -0400 |

Just use -suest-. Use the fact that -reg- without an argument is equivalent to estimating the mean. ******************** webuse income, clear svyset famid svy: reg inc if male estimates store Male svy: reg inc if !male estimates store Female suest Male Female nlcom _b[Male:_cons]/_b[Female:_cons] ************************* Steve 2010/4/23 Roman Kasal <kasal@trexima.cz>: > yes, the year is another survey (different time; the years cannot be pooled because of degrees of freedom) and is included in strata. > > so there is no solution for this case? just manually? > > -----Original Message----- > From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels > Sent: Friday, April 23, 2010 1:32 PM > To: statalist@hsphsun2.harvard.edu > Subject: Re: Re: st: RE: AW: ratio function > >> "svy: mean wage, over(year)" is not equal "svy: mean wage if year==2009" > > The "if statement" is incorrect, unless year was a stratification > variable that you identified to Stata. > > -nlcom- after -svy: mean-, over(year), is the proper approach. > > > 2010/4/23 Roman Kasal <kasal@trexima.cz>: >> ok, for this purpose I agree, that is ok...but what about if I want to calculate SE of Mean in years 2009 and 2008 and then ratio with SE of the means? >> >> the problem is that CI of >> "svy: mean wage, over(year)" is not equal "svy: mean wage if year==2009" >> for the year 2009 because of different degrees of freedom (SE's are equal), the first command gives wrong CI. >> >> is any elegant solution to handle this in Stata with "nlcom" or do I have to calculate it manually? >> >> thank you >> >> -----Original Message----- >> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels >> Sent: Thursday, April 22, 2010 3:08 PM >> To: statalist@hsphsun2.harvard.edu >> Subject: Re: Re: st: RE: AW: ratio function >> >> The degrees of freedom are correct. See any sampling text. >> >> Briefly: To identify a subpopulation, each observation in the sample >> receives a 0-1 indicator variable d. If X is the numerator variable >> and Y is the denominator variable, the numerator for the ratio of is >> the sum *over the entire sample* of Z_x = d *X and the denominator is >> the sum of Z_y = d * Y. The standard errors are based on variability >> in the Z's, including the zero values. >> By the way, the standard errors formulas are valid only if the >> expected number of observations in a subpopulation is at least 20. >> >> Steve >> >> 2010/4/22 Roman Kasal <kasal@trexima.cz>: >>> thank you for the code, but I have found a problem: >>> >>> if I calculate over(foreign) the bound are enumerated with "e(N_psu)-e(N_strata)" degrees of freedom, but not for each foreign (degrees of freedom are for whole dataset) and this is wrong I assume. >>> >>> thank you >>> >>> -----Original Message----- >>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels >>> Sent: Friday, April 02, 2010 2:58 PM >>> To: statalist@hsphsun2.harvard.edu >>> Subject: Re: Re: st: RE: AW: ratio function >>> >>> Roman >>> Perhaps we misunderstand what you are asking for. I We have been >>> assuming that you want the ratio of the means of two variables >>> ("columns"?) measured possibly on the same person. Perhaps you want >>> the ratio of the means of one variable for two subpopulations. Both >>> analyses will ignore missing values. >>> >>> If this is not what you desire, then please demonstrate by hand what >>> you do want on a small, non-survey data set.. Also I'd like to know >>> which R function does what are asking for >>> >>> The following do file computes the ratio of means with CI and then >>> does the same for the log ratio and transforms to the original scale. >>> >>> -Steve >>> >>> >>> **************************CODE BEGINS************************** >>> capture program drop _all >>> program antilog >>> local lparm el(r(b),1,1) >>> local se sqrt(el(r(V),1,1)) >>> local bound invttail(e(df_r),.025)*`se' >>> local parm exp(`lparm') >>> local ll exp(`lparm' - `bound') >>> local ul exp( `lparm' + `bound') >>> di "parm =" `parm' " ll = " `ll' " ul = " `ul' >>> end >>> >>> sysuse auto, clear >>> svyset _n >>> svy: mean mpg, over(foreign) >>> nlcom (myratio1: _b[Domestic]/_b[Foreign]) //ratio >>> nlcom (myratio2: log(_b[Domestic]/_b[Foreign])) // log ratio >>> // Confidence interval of last -nlcom- on antilog scale >>> antilog >>> ***************************CODE ENDS*************************** >>> >>> >>> >>> . >>> >>> On Fri, Apr 2, 2010 at 2:37 AM, Roman Kasal <kasal@trexima.cz> wrote: >>>> I don't agree...so how to do it when you want to find out ratio between >>>> years, male X female, ...? So there is no solution? Just to keep N,mean, >>>> SE, degrees of freedom, N_strata, N_psu, .... and calculate it manually? >>>> I think it is not appropriate solution, at least to have it as an >>>> option. I think there is missing a lot with complex survey in Stata and >>>> complex survey is needed for almost every survey research, even freeware >>>> R-project is better equipped :( >>>> >>>> so have a hope Stata will get it soon....immediately we are buying it >>>> again :) >>>> >>>>> >>>>> >>>> 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 >>>> >>>> >>>> * >>>> * 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/ >>>> >>> >>> >>> >>> -- >>> 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/ >>> >>> * >>> * 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/ >>> >> >> >> >> -- >> 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/ >> >> * >> * 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/ >> > > > > -- > 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/ > > * > * 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/ > -- 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/

**Follow-Ups**:**Re: Re: st: RE: AW: ratio function***From:*Steve Samuels <sjsamuels@gmail.com>

**References**:**Re: Re: st: RE: AW: ratio function***From:*"Roman Kasal" <kasal@trexima.cz>

**Re: Re: st: RE: AW: ratio function***From:*Steve Samuels <sjsamuels@gmail.com>

**RE: Re: st: RE: AW: ratio function***From:*"Roman Kasal" <kasal@trexima.cz>

**Re: Re: st: RE: AW: ratio function***From:*Steve Samuels <sjsamuels@gmail.com>

**RE: Re: st: RE: AW: ratio function***From:*"Roman Kasal" <kasal@trexima.cz>

**Re: Re: st: RE: AW: ratio function***From:*Steve Samuels <sjsamuels@gmail.com>

**RE: Re: st: RE: AW: ratio function***From:*"Roman Kasal" <kasal@trexima.cz>

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