Hello,
I am using Stata 9.2.
I am running clogit on a 1:20 matched study for telemetry steps (sampled_path) as mentioned previously. I am clustering on individual animal to produce robust SEs.
I noticed that when I use the cluster option, I get the Wald Chi output for my model and when I don't cluster I get a LR chi2 output. Can someone briefly explain why these change with cluster options or point me to a discussion/overview of this?
Are there implications in reporting one over the other? I noticed I get the LR chi2 from -fitstat- after -clogit-. Biologically, clustering on individual animal makes much more sense so I would prefer to use this.
Either way, these example models are significant correct?
Best,
Cheryl
*******************************************
OUTPUT
1. clogit sampled_path rdens2k_max trees_mean nonveg_mean, group( uidstep) cluster( uidpath) nolog
Conditional (fixed-effects) logistic regression Number of obs = 11613
Wald chi2(3) = 72.70
Prob > chi2 = 0.0000
Log pseudolikelihood = -1673.8298 Pseudo R2 = 0.0058
(Std. Err. adjusted for 5 clusters in uidpath)
------------------------------------------------------------------------------
| Robust
sampled_path | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
rdens2k_max | .2901546 .105544 2.75 0.006 .0832921 .497017
trees_mean | .4624635 .3109852 1.49 0.137 -.1470563 1.071983
nonveg_mean | .9611335 .8892528 1.08 0.280 -.78177 2.704037
------------------------------------------------------------------------------
2. clogit sampled_path rdens2k_max trees_mean nonveg_mean, group( uidstep) nolog
Conditional (fixed-effects) logistic regression Number of obs = 11613
LR chi2(3) = 19.58
Prob > chi2 = 0.0002
Log likelihood = -1673.8298 Pseudo R2 = 0.0058
------------------------------------------------------------------------------
sampled_path | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
rdens2k_max | .2901546 .0774408 3.75 0.000 .1383734 .4419357
trees_mean | .4624635 .2151835 2.15 0.032 .0407116 .8842154
nonveg_mean | .9611335 .3174182 3.03 0.002 .3390053 1.583262
------------------------------------------------------------------------------
***********************************************
Cheryl Chetkiewicz
P.O. Box 60208
Palo Alto, CA, 94306
USA
Telephone: 650-331-0069
E-Mail: [email protected]
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