choice-metrics.com

Dear Ngene Team,

I am coding a fractional factorial design with two modes, A and B. I tried to apply a multiplier of 1.5 to one of the coefficients, b4, but Ngene did not seem to recognize the syntax. it returned the warning message: Error: Wrong suffix '.5' was used. Please find my code below. I'd appreciate any advice and guidance you may have. Thank you!

;alts = A, B
;rows = 72
;fact
;model:

U(A) = b1 + b2 * costA[5,10,15] + b3 * waitA[2,5,10] + b4 * timeA[10,20,30] /
U(B) = b2 * costB[1,2,3] + b4 * 1.5 * waitB[3,6,9] + b4 * timeB[20,40,60]

Three ways of doing this:

1. You can multiply the levels with 1.5, i.e. waitB[4.5,9,13.5]
2. You can divide b4 by 1.5 after model estimation
3. You can make this multiplier an attribute, i.e. b4 * mult[1.5] * waitB[3,6,9]

Note that these utility functions are essentially ignored when you create a random factorial design, they become important when you look for an efficient design.

Michiel