[Limdep Nlogit List] Test if blocks in the design created a bias.

Damien Jourdain djourdain at ait.asia
Mon Jun 12 13:18:26 AEST 2017


Dear all, 

 

We have conducted a discrete choice experiment using a D-efficient design
with 18 scenarios. As we were concerned that 18 scenarios would create too
much burden for respondents, we decided to create 3 blocks of 6 scenarios.

 

The population of the 3 blocks were chosen to be as similar as possible, but
since not all people received the same scenarios, we would like to test
whether we haven't created a bias. 

 

It is an unlabeled experiment with one status quo option. We have introduced
a dummy variable ASC (1 when SQ, 0 other alternative), and two dummy
variables for block2 and block3. 

 

We want to test that blocks did not introduce some bias, so we are testing
the interactions of blocks with the ASC variable (as we would test the
influence of socio-economic variables)

 

? MNL Model

NLOGIT; 

    ; Choices = 1,2,3

    ; Lhs = choice

    ; Rhs = asc, asc*block2, asc*block3 , prim, wbird, iweed, fecos 

$

 

If the coefficient associated to asc*block1 and asc*block2 are not
significantly different from zero, can we say that the block did not
introduce biases?   Or should we use another test?

 

Would this formulation still work if we were using effect coding for both
ASC and block2 and block3? 

 

Best,

 

Damien

 

 

Dr. Damien Jourdain

Agricultural and Natural Resources Economist

Visiting Assistant Professor

Asian Institute of Technology / CIRAD G-EAU

Natural Resource Management / Water Engineering and Management

 

mail: djourdain at ait.asia

 

web GEAU : www.g-eau.net <http://www.g-eau.net/>  

web NRM :  <http://www.nrm.ait.asia/> www.nrm.ait.asia

 

 

 



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