[Limdep Nlogit List] Help with clogit model

[Manit Satitsamitpong]

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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