Thanks Kit and Nick,
I just tried Kit's suggestion. One variable has two categories and the
other has three. My test is to determine if there is a difference between
cases with and without Autism Diagnosis (2) using an ordered severity
measure with three levels (none, mild or severe). Using your suggestion, I
obtained the following result. Does this look like the p value is
calculated correctly?
Deidra
. tab autism_dx kerr_breath_score, all
| Kerr Score for Disturbed Awake
Initially Diagnosed | Breathing Rhythm
with Autism | None Mild Severe | Total
--------------------+---------------------------------+----------
No Autism Diagnosis | 75 109 76 | 260
Autism Diagnosis | 11 29 15 | 55
--------------------+---------------------------------+----------
Total | 86 138 91 | 315
Pearson chi2(2) = 2.5711 Pr = 0.277
likelihood-ratio chi2(2) = 2.6204 Pr = 0.270
Cram�r's V = 0.0903
gamma = 0.0759 ASE = 0.116
Kendall's tau-b = 0.0324 ASE = 0.050
. ret li
scalars:
r(N) = 315
r(r) = 2
r(c) = 3
r(chi2) = 2.571055140705914
r(p) = .2765046694792958
r(chi2_lr) = 2.620364965212246
r(p_lr) = .2697708234098308
r(CramersV) = .0903442295432575
r(gamma) = .0758665794637018
r(ase_gam) = .1163419665428843
r(taub) = .0324087958656579
r(ase_taub) = .0497834038046439
. di r(taub) / r(ase_taub)
.65099598
. scalar z=r(taub)/r(ase_taub)
. display "z= " z " with p-value " normden(1-z)
z= .65099598 with p-value .37537099
On 5/12/06 8:22 PM, "Kit Baum" <[email protected]>
> Deidra wants to retrieve the p-value and Kendall tau-b score from a
> tab of two variables.
>
>
> . tab anxiety depress,all
>
> | DEPRESS
> ANXIETY | 1 2 3 | Total
> -----------+---------------------------------+----------
> 1 | 8 1 0 | 9
> 2 | 14 42 3 | 59
> 3 | 3 21 11 | 35
> 4 | 0 1 3 | 4
> -----------+---------------------------------+----------
> Total | 25 65 17 | 107
>
> Pearson chi2(6) = 46.1892 Pr = 0.000
> likelihood-ratio chi2(6) = 40.9054 Pr = 0.000
> Cram�r's V = 0.4646
> gamma = 0.7778 ASE = 0.087
> Kendall's tau-b = 0.4951 ASE = 0.070
>
> . return list
>
> scalars:
> r(N) = 107
> r(r) = 4
> r(c) = 3
> r(chi2) = 46.18917309609633
> r(p) = 2.71459405298e-08
> r(chi2_lr) = 40.90537799483023
> r(p_lr) = 3.02263811177e-07
> r(CramersV) = .4645828854557538
> r(gamma) = .7777777777777778
> r(ase_gam) = .087050646901156
> r(taub) = .4950723482288552
> r(ase_taub) = .0704364215558283
>
> If she wants the p-value of Kendall's tau-b, it can be easily
> calculated (if indeed taub is ~N(0,1)) from what is available in the
> return list:
>
> . scalar z=r(taub)/r(ase_taub)
>
> . display "z= " z " with p-value " normden(1-z)
> z= 7.0286414 with p-value 5.114e-09
>
>
>
> Kit Baum, Boston College Economics
> http://ideas.repec.org/e/pba1.html
> An Introduction to Modern Econometrics Using Stata:
> http://www.stata-press.com/books/imeus.html
>
>
>
> *
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> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
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