Re: st: Comparing bootstrapped estimates across two models

[Steven Samuels <sjsamuels@gmail.com>]

-

Since you want to compare results from two commands run on the same  
data, you will need to write a single program that bootstraps both.   
For an example, see: http://www.ssc.wisc.edu/sscc/pubs/4-27.htm.

The quantity to bootstrap would be wtp1 - wtp2. I don't know anything  
about this field, but if  WTPs are always positive or always negative,  
perhaps their ratios are more informative; if so, consider  
bootstrapping log(wtp1/wtp2).

I suggest that you base inference on the built-in bootstrap confidence  
intervals.  If you want to do a hypothesis test, you might have to  
build your own; see e.g. http://portal.acm.org/citation.cfm?id=1280646  
and an older paper: Peter Hall and Susan R. Wilson Two Guidelines for  
Bootstrap Hypothesis Testing, Biometrics Vol. 47, No. 2 (Jun., 1991),  
pp. 757-762.

Steve
sjsamuels@gmail.com



On Feb 4, 2011, at 12:47 PM, Matthew Wibbenmeyer wrote:

Hi all,

I'm engaged in a choice modeling study in which wildfire managers were
asked to select their **preferred** management strategy and their
**expected** strategy  given current political and social constraints.
I want to compare willingness-to-pay values derived from two models
with different dependent variables: choice_expected and
choice_preferred. WTP values are ratios between coefficients so they
have no distribution and a distribution must be estimated using
bootstrapping (or parametric bootstrapping).

My question has two parts:
1) What formal test can I use to test the significance of the
difference between bootstrapped WTP estimates from two models with
different dependent variables?
2) How can I implement this following my bootstrap commands, which
look like this:

bootstrap wtp1 = ((-1)*(_b[homes]/_b[cost])), reps(100) seed(12345)
cluster(obsid) dots: ///
clogit choice_exp homes watershed aviationhours grounddays duration  
cost ///
, group(obsid)

bootstrap wtp2 = ((-1)*(_b[homes]/_b[cost])), reps(100) seed(12345)
cluster(obsid) dots: ///
clogit choice_pref homes watershed aviationhours grounddays duration  
cost ///
, group(obsid)

Thanks in advance for any help anyone can offer!

Matt Wibbenmeyer
USDA Forest Service
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