Re: st: Kendalls tau-b difference between ktau and tabulate taub

[Roberto Ferrer <refp16@gmail.com>]

This works fine for me:

*----------------- begin code -------------------

clear all
set more off

input x y
3 5
6 7
2 3
9 4
7 5
4 2
end

ktau x y, stats(taub se)

tabulate x y, taub

*------------- end code -----------------------

On Sat, Jan 25, 2014 at 12:01 PM, Kornak, John <john.kornak@ucsf.edu> wrote:
> Hi Statalist members,
>
> I am trying to figure out why I get different results using the stata function ktau versus tabulate with the taub option.
>
> For example if I have the following dataset
>
> . list
>
>      +-------+
>      | x   y |
>      |-------|
>   1. | 3   5 |
>   2. | 6   7 |
>   3. | 2   3 |
>   4. | 9   4 |
>   5. | 7   5 |
>   6. | 4   2 |
>      +-------+
>
> .
>
> then using ktau I get
>
> . ktau x y, stats(taub se)                      [I have snipped the output to the relevant parts below]
>
> Kendall's tau-b =       0.1380
>     SE of score =       5.228   (corrected for ties)
> .
>
> Within tabulate; (tabi 3 6 2 9 7 4\5 7 3 4 5 2, taub) I get
>
>  Kendall's tau-b =  -0.1667  ASE = 0.115
>
> If I transpose rows and columns I still get the same (i.e. with tabi 3 5\6 7\2 3\9 4\7 5\4 2, taub)
>
> Even cases like correlating 1,2,…,n with itself (tabi 1 1\2 2\3 3\4 4\ 5 5, taub) in tabulate gives an unexpected answer to me of 0.
>
> I am using Stata 13 on a macbook pro running OS X v. 10.8.5.
>
> Any insights into why I get differing answers would be very much appreciated. I expect I am misinterpreting what taub is supposed to be doing in tabulate.
>
> Thanks for any help
>
> John
>
>
> ----------------------------------------------------
> John Kornak, PhD
> Associate Professor in Residence
> Department of Epidemiology and Biostatistics
> University of California, San Francisco
> UCSF Box 0560
> 185 Berry Street, Lobby 5, Suite 5700
> San Francisco, CA 94107-1762
> Tel: 415-514-8028
> Fax: 415-514-8150
> Email: john.kornak@ucsf.edu
>
>
>
>
>
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