[Limdep Nlogit List] Help with clogit model

Thu Apr 29 15:37:53 EST 2010

Dear Professor,

I am just curious if in the futre I want to do similar research and I
divide the size of choice set using blocking technique, is it possible
to run using clogit or nlogit in this case then?  Also do you have any
sample code on LIMDEP to do so?  Thank you very much.

Best regards,
Manit Satitsamitpong

On 29 เม.ย. 2010, at 4:36, Vassilopoulos Achilleas <avassilopoulos.aua at gma
il.com> wrote:

> Manin,
>
>
>
> I'm sorry but I misunderstood your first email. Now I see that what
> you have
> created through SPSS is a design for conjoint analysis and not for a
> choice
> experiment. So this is completely different from the design you
> would use
> for a CE. Those 16 'profiles' you have now may only be used for
> ranking or
> rating, and even in this case you should use all 16 together.
>
> So my answer to your question is no; given the random partition of
> the cards
> you have done, I am not sure ANY model can give you the desirable
> parameter
> estimates; I can assure you though, that the conditional logit will
> not.
>
>
>
> Good luck,
>
> _____________ - _______________
>
>
>
> Achilleas Vassilopoulos
>
>
>
> Agricultural University of Athens,
>
> Dept. of Agricultural Economics and Rural Development,
>
> Lab. of Political Economy and European Integration.
>
> Iera Odos 75, 11855, Athens, Greece
>
>
>
> Tel: (+30) 210-5294726
>
> Fax: (+30) 2105294786
>
>
>
>
>
> -----Original Message-----
> From: limdep-bounces at limdep.itls.usyd.edu.au
> [mailto:limdep-bounces at limdep.itls.usyd.edu.au] On Behalf Of Manit
> Satitsamitpong
> Sent: Wednesday, April 28, 2010 6:05 PM
> To: Limdep and Nlogit Mailing List
> Subject: Re: [Limdep Nlogit List] Help with clogit model
>
>
>
> Dear Professor Vassilopoulos,
>
>
>
>
>
> Thank you very much for your detailed answer.  The way I came up
> with the 16
>
> alternatives is via SPSS orthogonal design command.  Then I splitted
> into 4
>
> choice sets to reduce the size of cards as you might have thought by
>
> arbitrary process without using blocking technique.  In this case,
> is there
>
> any other ways I could measure the parameter estimates for each
> attribute?
>
> Thank you very much for your help.
>
>
>
> Best regards,
>
> Manit Satitsamitpong
>
> On Wed, Apr 28, 2010 at 11:03 PM, Achilleas Vassilopoulos <
>
> avassilopoulos.aua at gmail.com> wrote:
>
>
>
>> Dear Martin,
>
>>
>
>> When respondents choose between air, bus, train etc., we are
>> talking about
>
>> a
>
>> labeled experiment whereas yours is an unlabeled one. You can easily
>
>> estimate unlabeled choice experiments using Nlogit by just assigning
> random
>
>> names in each of your alternatives (e.g A, B, C, D). Note that
>> although A,
>
>> B, C and D will be different for every respondent, since you do not
> include
>
>> a constant term in your model (i.e "ONE" in your Rhs variables) the
> results
>
>> you get are the generic parameter estimates of the utility
>> associated with
>
>> each attribute or attribute level (i.e price, video, setup_cost,
>
>> enhance_service).
>
>>
>
>> What I'm not sure about is how have you ended up with these 16
> alternatives
>
>> (combinations as you refer to)? Where they a result of  a full or
>
>> fractional
>
>> factorial design or you have assigned the attributes and the
>> attributes'
>
>> level of each alternative  arbitrarily or by experience?  In the last
> case,
>
>> there is no possible way to estimate such a model in an efficient and
>
>> unbiased manner since your Rhs variables are probably highly
>> correlated
> and
>
>> the parameters you'll get (if any) will be completely
>> uninformative. At
>
>> last, instead of  just splitting all 16 possible alternatives in 4
>> choice
>
>> sets to reduce the size of cards, you need to employ blocking
>> techniques
> in
>
>> your experimental design.
>
>>
>
>> I hope that helps,
>
>> _____________ - _______________
>
>>
>
>> Achilleas Vassilopoulos
>
>>
>
>> Agricultural University of Athens,
>
>> Dept. of Agricultural Economics and Rural Development,
>
>> Lab. of Political Economy and European Integration.
>
>> Iera Odos 75, 11855, Athens, Greece
>
>>
>
>> Tel: (+30) 210-5294726
>
>> Fax: (+30) 2105294786
>
>>
>
>>
>
>>
>
>> -----Original Message-----
>
>> From: limdep-bounces at limdep.itls.usyd.edu.au
>
>> [mailto:limdep-bounces at limdep.itls.usyd.edu.au] On Behalf Of Manit
>
>> Satitsamitpong
>
>> Sent: Wednesday, April 28, 2010 3:21 PM
>
>> To: limdep at limdep.itls.usyd.edu.au
>
>> Subject: [Limdep Nlogit List] Help with clogit model
>
>>
>
>> Dear All,
>
>>
>
>> I am very new in this area. I really hope someone could help me
>> with the
>
>> command or concept about the choice model that I am facing right now.
>
>>
>
>>
>
>> Suppose I would like to estimate customer preferences and the
>> relative
>
>> importance of service factors of IPTV such as price per month
>> (range of
>
>> price), video on demand feature (high or low), setup cost (high or
>> low),
>
>> enhanced service (yes or no),and other 2 factors.  Then I created
>> say 16
>
>> profiles of combinations of those factors (conjoint questions)  for
>
>> respondents to answer.  I understood that if I asked respondents to
>> rank
>
>> all
>
>> those 16 profiles (combinations) then I can use SPSS to run the
>> conjoint
>
>> analysis and then I can calculate the importance of each factor.
>
>>
>
>> My question here is what if I break down those 16 profiles into 4
>> choices
>
>> sets with each set contains 4 profiles (combinations) and then ask
>
>> respondents to choose the best choice (alternative) among each
>> choice set.
>
>> In this case, I don't think I can use clogit command to do so.
>> Because
>
>> clogit command asks me to provide the choice list (specific names
>> of each
>
>> choice) but in this case I don't have a specific name for each
>> combination
>
>> of choice set.
>
>>
>
>> clogit   ;lhs = choice
>
>>           ;Rhs = price, video, setup_cost, enhance_service
>
>>          ;Choices = ????
>
>> $
>
>>
>
>> Here I don't know what to use as the parameters for Choices since all
> those
>
>> 16 combinations are different, unlike the transportation mode (air,
>> bus,
>
>> car, train) given in Professor Greene's book.  Is there any way for
>> me to
>
>> use LIMDEP or other software to run this data given the data that i
>> have
>
>> (choice data instead of ranking data).   Thank you very much.  I am
>> really
>
>> appreciated your time for reading this mail.
>
>>
>
>>
>
>> Best regards,
>
>> Manit Satitsamitpong
>
>> _______________________________________________
>
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>
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>
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>
>>
>
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>
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>
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>
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>
>>
>
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