I am wondering how Lighthouse comes up with the scale of raw utilities:

1) In particular, I am interested how you set/define the “zero-line” in effects-coding?

2) Why isn’t the NONE-threshold (of an included dual-response none-option) the “zero-line”? Can I make the NONE value (which in my case is negative) the “zero-value” by simply adding its value to every level of each attribute?

3) How could one “normalize” part-worths of different estimations so that they use the same scale, i.e., that one could directly compare results among different estimation strategies or sub-samples (e.g., performing a ttest)?

Thank you in advance for your support!

Best regards

To 1) But the utilities can be centered to zero in many ways (i.e. by adding constants, see 2.), so how do you come up with that particular "zero"? And how would you interpret it?

To 2) If the NONE threshold would be the "zero", I could interpret a negative level as: "ceteris paribus this level decreases the probability of an alternative being chosen/bought". While I could not come up with that conclusion if the part-worth is between the NONE threshold and the zero-value(?). Or am I getting something wrong here?

So, is it correct to add the none-value to every attribute level in order that the NONE-threshold becomes zero?

To 3) As I understand SSI's "zero-centered differences" they also put weights on certain respondents, thus relative mean preferences could be different to relative means of raw utilities(?). How could I normalize and compare raw utilities without the obstacle of assigning different weights?

Thanks again!