Status quo levels in discrete choice experiment

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Re: Status quo levels in discrete choice experiment

Postby JvB » Sat May 14, 2022 11:49 pm

Dear Michiel,

so far I´ve used dummy coding for my estimations of the above mentioned model.
Is there any indication to use effects coding instead of dummy coding?
I´ve seen that some papers are using effects coding for categorical variables but am not sure if that might also make sense for my model.
I suppose no, because effects coding prevents from choosing the reference level arbitrarily, but as I have a fixed status quo dummy coding with SQ levels as reference levels seems to make most sense?!

Thankful for any information from your point of view!
Thanks and best,
J.
JvB
 
Posts: 45
Joined: Mon Mar 22, 2021 12:17 am

Re: Status quo levels in discrete choice experiment

Postby JvB » Sat May 14, 2022 11:51 pm

Sorry, this is the respective code:

Design
;alts = alt1*, alt2*, SQ*
;rows = 18
;block = 2
;eff = (mnl,d)
;alg = mfederov
;require:
SQ.amount = 3, SQ.period = 3
;reject:
alt1.amount = 3 AND alt1.period = 3,
alt2.amount = 3 AND alt2.period = 3
;model:
U(alt1) = b1[-0.0001] * contrib[1.8,2.5,3.2](6,6,6)
+ b2.dummy[0.0003|0.0002|0.0001] * amount[0,1,2,3] ? 0 = 300, 1 = 600, 2 = 900, 3 = unlimited amount
+ b3.dummy[0.0003|0.0002|0.0001] * period[0,1,2,3] ? 0 = 12, 1 = 42, 2 = 72, 3 = unlimited period
/
U(alt2) = b1 * contrib
+ b2 * amount
+ b3 * period
/
U(SQ) = b0[0]
+ b1 * contrib_sq[1.6]
+ b2 * amount
+ b3 * period
$
JvB
 
Posts: 45
Joined: Mon Mar 22, 2021 12:17 am

Re: Status quo levels in discrete choice experiment

Postby Michiel Bliemer » Sun May 15, 2022 11:49 am

There is no real difference between dummy and effects coding as shown by Daly & Dekker & Hess (2016), so using dummy coding is perfectly fine and will make it easier to interpret parameters.

Daly, Dekker and Hess (2016) Dummy coding vs effects coding for categorical variables: Clarifications and extensions. Journal of Choice Modelling. https://www.sciencedirect.com/science/article/abs/pii/S1755534516300781

Michiel
Michiel Bliemer
 
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Joined: Tue Mar 31, 2009 4:13 pm

Re: Status quo levels in discrete choice experiment

Postby JvB » Tue May 17, 2022 1:15 am

Thank you very much for re-confirming, Michiel!
JvB
 
Posts: 45
Joined: Mon Mar 22, 2021 12:17 am

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