Number of blocks in main survey

[firat85]

Dear all,

I'm about to start my main survey with a sample size of 600-700 participants that I hope to reach. My question is, would it provide enough variation for this sample size if I create 24 choice sets in total as three blocks consist of 8 choice sets? is there any criteria for this issue? Some papers in literature apply more for ex. 80 choice sets in 10 blocks.

[Michiel Bliemer]

That depends on the number of coefficients you are using as well as the number of alternatives in your choice model.

The number of choice tasks S needs to satisfy:

S*(J-1) >= K

where J is the number of alternatives and K is the number of coefficients you are estimating (including for dummy coded variables, interaction effects, etc).

The smallest S that satisfies the above is the MINIMUM number of choice tasks you need in your design (before blocking). But generally you will want to use a larger design than that to have enough variation, so you could choose to use something like 2*S, 3*S or 4*S to make sure that you have enough variation.

You may want to refer to Sandor and Wedel (2005), https://journals.sagepub.com/doi/abs/10.1509/jmkr.42.2.210.62285.

Michiel

[firat85]

Thank you for your answer Mr. Bliemer.