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RE: st: calculate probability for clogit


From   Patty_FARE_Guelph Apichaya <pattria_ft@hotmail.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   RE: st: calculate probability for clogit
Date   Fri, 23 Apr 2010 01:34:08 +0000

Hi,

  I try to use -asclogit- but it has to have more than 2 alternatives in 1 choice set, so I cannot use this command in my analysis.
 For the choice design, I use SAS software to design the pair of alternative and combination of factors in order to balance and give the optimal sets. I use clogit to analyze my choices and I want to know how I calculate probability the people choose each alternative in choice set. 

if I want to calculate personal factors, should I use -xtlogit- or which command it is appropriate? 

Thanks

Apichaya Lilavanichakul
MSc. Candidate
Department of Food Agricultural and Resource Economics
Ontario Agricultural College
University of Guelph
Guelph, ON



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