[Limdep Nlogit List] Help with clogit model

Manit Satitsamitpong manit835 at gmail.com
Thu Apr 29 06:33:52 EST 2010


Dear Professor,

Thank you very much for your answer and explanation. I guess I have to
use this as my lesson and try to collect data one more time using all
16 profiles and possible use rating for ranking as a way to collect
the data.  Again I am really appreciated the time you gave to answer
my questions.

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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