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Re: st: calculate probability for clogit


From   Steve Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: calculate probability for clogit
Date   Tue, 20 Apr 2010 16:12:44 -0400

I know almost nothing about discrete choice experiments, so please
read the following comments with that in mind.

1. -asclogit-  might be a better choice than -clogit-, as it will more
easily include  person-level variables like gender, income, and sex.

2. Your setup does not identify the individual in any way. The
examples for -asclogit- and -clogit-  all use the individual as the
case or group variable. As "set" has only four levels, perhaps you can
include it as a person-level variable.

3. The examples in -asclogit- consider  alternatives based on one
attribute (factor).  You have three factors  and these generate 12 (=
3 x 2 x 2)  possible options, with 66  possible pairwise comparisons.
You selected 32 of these,  divided into four sets.  I'm curious--is
there  a reference for this experimental design?  Is the choice of
comparisons and construction of the sets  optimal or balanced in some
sense?

4. For predicted probabilities, use  the  -pr- option in -asclogit- .

Steve

On Tue, Apr 20, 2010 at 9:39 AM, Patty_FARE_Guelph Apichaya
<pattria_ft@hotmail.com> wrote:
> Hi all,
>
>       I use STATA to analyze discrete choihce experiment. My choice design has 32 choice sets with each 2 options (A and B). Each option include 3 factors: price (13,15,17), brand (AA,BB), labeling (animal,plant). The choice set will look like this.
>                  Option A                           OptionB
>     price                    13                                       15
>     brand                   AA                                        BB
>    labeling          animal                               plant
>
>            From 32 choice sets is divide into 4 block with each 8 choice sets. Each individual (100 individuals) get 1 block (8 choice sets) and ask to choose between option A or B.
>
>     choice = 1 chosen option, 0 not chosen option
>     set = same for two alternatives for each set i.e. there are 32 choice sets, it is repeated number from 1 to 32 and start it
>           again for the next 32 choice sets.
>
> This is the code; clogit choice price brand labeling, group(set)
>
> I also want to include individual characteristics; gender, income, age. how I can do it?
>
> How I can calculate the probability from people choosing choice?
>
> Any suggestion would be great.
> Pat
>
>
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-- 
Steven Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
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