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From |
Cameron McIntosh <[email protected]> |

To |
STATA LIST <[email protected]> |

Subject |
RE: st: Confirming whether a variable is binary or continuous |

Date |
Sun, 18 Mar 2012 23:02:42 -0400 |

I think that the only way to decide how to proceed is to first approach this issue conceptually (i.e, think about it) -- based on your content area expertise, is the covariate in question truly binary (qualitative) or do the observed categories merely discretize a latent continuous process? If the former, you can use observed categorical variable methodology to examine the covariate distributions by treatment group. (e.g., chi-square tests of independence and related methods for contingency tables); if the latter, then you may be into tetrachorics and the like. MacDonald, P.L., & Gardner, R.C. (2000). Type I Error Rate Comparisons of Post Hoc Procedures for I j Chi-Square Tables. Educational and Psychological Measurement, 60(5), 735-754. Bentler, P.M. (2011). Can Interval-level Scores be Obtained from Binary Responses? UCLA Preprint #622.http://preprints.stat.ucla.edu/622/Bentler%20Interval%20Scores%20from%20Binary%20Responses.pdf Ulrich, R., & Wirtz, M. (2004). On the correlation of a naturally and an artificially dichotomized variable. British Journal of Mathematical and Statistical Psychology, 57(2), 235–251. Ledesma, R.D., Macbeth, G., & Valero-Mora, P. (2011). Software for Computing the Tetrachoric Correlation Coefficient. Revista Latinoamericana de Psicología, 43(1), 181-189. http://openjournal.konradlorenz.edu.co/index.php/rlpsi/article/viewFile/459/463 Greer, T., Dunlap, W.P., & Beatty, G.O. (2003). A Monte Carlo Evaluation of the Tetrachoric Correlation Coefficient. Educational and Psychological Measurement, 63(6), 931-950. Bonett, D.G., & Price, R.M. (2005). Inferential Methods for the Tetrachoric Correlation Coefficient. Journal of Educational and Behavioral Statistics, 30(2), 213-225. Long, M.A., Berry, K.J., & Milke, P.W., Jr. (2009). Tetrachoric Correlation: A Permutation Alternative. Educational and Psychological Measurement, 69(3), 429-437. Genest, C., & Lévesque, J.-M. (2009). Estimating correlation from dichotomized normal variables. Journal of Statistical Planning and Inference, 139(11), 3785-3794. Choi, J., Peters, M., & Mueller, R.O. (2010). Correlational analysis of ordinal data: from Pearson’s r to Bayesian polychoric correlation. Asia Pacific Education Review, 11(4), 459-466. Cam > Date: Mon, 19 Mar 2012 00:28:27 +0000 > Subject: Re: st: Confirming whether a variable is binary or continuous > From: [email protected] > To: [email protected] > > Your program just echoes its own input, confirming that what you > specify is a binary variable is indeed binary and what you specify is > a continuous variable is indeed continuous. It does no checking > whatsoever. > > I am puzzled about why you think that is useful and indeed in what > sense it is a solution to your original problem. > > Nick > > On Sun, Mar 18, 2012 at 5:07 PM, Bert Jung <[email protected]> wrote: > > > Thanks all for these helpful insights. I wanted to share my solution > > which, if clumsy, works for me. The basic idea is to check whether a > > particular variable is part of the continuous or binary varlist and > > then proceed as appropriate. > > > > This approach keeps intact the order specified in varlist. I am > > collecting estimation output and wanted the order to remain as > > specified by the user. > > > > This is just a minimum working example, obviously various checks and > > balances are of order. > > > > Cheers Bert > > > > > > > > cap program drop varcheck > > program varcheck, nclass > > > > syntax varlist, contvars(varlist) binaryvars(varlist) > > > > * Loop over all variables in varlist; this approach keeps the order > > in -varlist- intact > > foreach v of local varlist { > > > > * (a) Is variable part of the variables specified in "contvars"? > > local contvar: list v in contvars > > > > if `contvar'==1 { > > di "`v' is specified as continuous variable" > > } > > > > > > * (b) Is variable part of the variables specified in "binaryvars"? > > local propvar: list v in binaryvars > > > > if `propvar'==1 { > > di "`v' specified as binary variable" > > } > > } > > > > end > > > > > > sysuse auto, clear > > > > varcheck mpg price foreign weight, contvars(mpg price weight) > > binaryvars(foreign) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Sun, Mar 18, 2012 at 7:40 AM, Alexander Jais <[email protected]> wrote: > >> Sorry, stimmt ist bei mir noch als to do - kommt die Woche. > >> > >> Bist wieder aus INdien zurück - wie wars? > >> > >> LG > >> Alex > >> > >> On 03/16/12, Bert Jung <[email protected]> wrote: > >> > >>> Dear Statalisters, > >>> > >>> I am writing a short program to make a balance table that compares > >>> covariates across a treatment and control group. I am looking for a > >>> way to confirm whether a variable is binary in order to use -prtest- > >>> for proportions rather than -ttest- for continous variables. > >>> > >>> One option is to check the actual data values and do -prtest- if there > >>> are only 0's and 1's. But a continuous but rare outcome could > >>> accidentally also take these values, e.g. the number of > >>> hospitalizations in the past 3 months. > >>> > >>> Is there a safer way to confirm that a variable is binary? > >>> > >>> Thanks for any pointers, > >>> Bert > > * > * 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**:

**References**:**st: Confirming whether a variable is binary or continuous***From:*Bert Jung <[email protected]>

**Re: st: Confirming whether a variable is binary or continuous***From:*Alexander Jais <[email protected]>

**Re: st: Confirming whether a variable is binary or continuous***From:*Bert Jung <[email protected]>

**Re: st: Confirming whether a variable is binary or continuous***From:*Nick Cox <[email protected]>

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