How to get "Neither" option appear on survey

[Donita]

Hi,
I am in the process of developing my DCE pilot. This project aims to determine healthcare provider preferences regarding Atrial Fibrillation screening. I have 3 alternatives (optA, optB, and opt-out) with 5 attributes (4 X 3 levels and 1 X 2 levels). I am considering an unlabelled design and I want to include the "opt-out" to mean that Participants don’t prefer the options presented and are not necessarily against AF screening. I want to employ a dual response approach where where respondents were first given three options, ‘A’, ‘B’ and ‘neither’ (unconditional response). If they selected ‘neither,’ they were presented with a forced choice between ‘A’ and ‘B’ (conditional response). However, I've been struggling to get the opt-out option on my survey. Can you please help? Please see the code below.

Design
;alts = optA*, optB*, optout
;rows = 21
;block = 3
;eff = (mnl,d)

;cond:
if (optA.screening = 1, optA.frequency =[2]),
if (optB.screening = 1, optB.frequency =[2])


;model:
U(optA)
= b1.dummy[0.001 | 0.002] * screening device[1, 2, 0]
+ b2.dummy[0.001 | 0.002] * frequency [1, 2,0]
+ b3.dummy[0.001 | 0.002] * population [1, 2, 0]
+ b4.dummy[-0.001] * incentives [1, 0]
+ b5.dummy[0.001 | 0.002] * costs [1, 2, 0]

/

U(optB)
= b1 * screening device
+ b2 * frequency
+ b3 * population
+ b4 * incentives
+ b5 * costs

$

Thank you!

[Michiel Bliemer]

An opt-out alternative does not show up in your experimental design because there is nothing to design for an opt-out alternative. It is simply an empty column with no attribute levels. Ngene accounts for the optout in generating an efficient design. If you want Ngene to show it in formatted scenarios, you can right-click in the scenario formatting editor and add a column to show an empty column. Some changes for your script:
* Add U(optout) = b0[0]
* Your attribute names cannot contain spaces, so you need to write screening, not "screening device"

In your survey instrument (SurveyEngine, Qualtrics, etc) you simply add an empty column as opt-out to your set of alternatives. If they select the opt-out in the unforced choice, you can follow up with a forced choice where only optA and optB are available. How to do to this in the survey instrument depends on the instrument and best to ask them.

Michiel