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When creating complex designs, I typically run several instances of NGENE using different values for ;RDRAWS and ;REP. Despite using the same ;RSEED, the efficiency measure changes when I evaluate a previously saved design or use it as a starting value. Is this a bug, or am I overlooking something ...

Dear Michiel,

Thanks for the reference to the paper. Did you mean this one:
Bliemer, M. C. J., and Rose, J. M., 2011. Experimental design influences on stated choice outputs: An empirical study in air travel choice. Transportation Research Part A: Policy and Practice, 45(1):63-79.
It actually only ...

Hi John,

Thanks for your reply.
The second attempt you report illustrates what is happening (every once in a while). I did this 100 times for different designs and observed that:
- this is less likely to happen in the case of the designs optimized for MNL (even though MXL is estimated using these ...

I hope to pick your brain (identify an error?) about a weird result I observed when running simulations with different design types.

Long story short - I generate efficient designs optimized for MXL or MNL, or OOD designs. I use these designs to produce artificial choice data (using MXL as data ...

Hi Michiel,

Thank you - this helps!

Mik

Hi Michiel,

Thanks for your reply. All clear.

I found this in the manual: 'Note that adding a second colon will generate discrete attribute levels, from the lower bound to the upper bound, with a step size specified after the second colon (e.g. [2:10:0.5]).' (p. 191) and I thought the algorithm ...

Hi John,

Thank you for very comprehensive and thorough reply.

Does this mean I can never have OOD design which would take ASCs into account or this only holds for ASCs for opt-out/sq alternatives?

Regarding the degrees of freedom - I know the formula and in fact NGENE warns about this and ...

Hi again - here is another problem I encountered, this time crashing NGENE:


design
; alts = alt1, alt2, alt3
; rows = 16
; block = 4
? ; bseed=179424673
; rseed=179424673
?; bdraws = halton(1000)
; rdraws = sobol(100)
; eff = (rppanel,d)
; rep = 400
? ; orth = ood
; start = initial_ood.ngd ...

Hi Guys,

I encountered the 'Something went unexpectedly wrong' error message for the following design:

design
; alts = alt1, alt2, alt3
; rows = 4
; orth = ood
; con
; model:
U(alt1) = bsq*SQ[-1] /
U(alt2) = bA1*A1[1,0]
+ bA2*A2[1,0]
+ bA3*A3[1,0]
+ bC*C[-0.25,-0.75,-1.25,-1.75] /
U(alt3 ...

I suppose specifying the seed for random draws would help. Try ;rseed (or ;bseed for Bayesian priors) in the manual.