Indicator weights in formative constructs

[langmach]

Dear All,

the model that I am currently working on consists mostly of variables with reflective indicators. Yet, there are two variables with formative indicators in the model. Different from most other formative modeled latent variables, I directly asked the informants how important each of the indicators is for them. (Hence, I have the empirical weights for each indicator!)
Take for example the variable project performance:

• How was the project performance on each of the following dimensions?
  How important was each dimensions for evaluating project performance?

But now comes the issue I am struggling with: How to handle such a variable in PLS? In my opinion I have two alternatives:
(1) Since I have the empirical weights for each dimension coming from the questionnaire, I could just use these weights to form an overall weighted index for the variable. In this case I would attach a single-item-index to the variable in the PLS-Model.
(2) Just like in alt. (1) I could use the empirical weights, but instead of forming an overall index, I could attach each indicator multiplied by its empirical weight to the latent variable. PLS would estimate the weights of the indicators (again?!?).

Personally, I think that alternative (1) is the way to go. The thing that bothers me in alternative (2) is that PLS will estimate the weights of the already! weighted indicators.

Could anyone give me his opinion on that issue???

Thanks a lot,

Chris

[Diogenes]

Hi Chris,
I agree with the first one, for using the "empirical weights", that I have understood that are comming from previous research or theory.
Best regards.
Bido

[langmach]

Hi Bido,

thanks for your response.

Just for clarification: I am thinking to derive the weights from the same questionnaire as the dimensions, not from previous research or theory. Just as explained in the variable on project performance above:

First, I ask the informants how the project performed on each of several dimensions. Afterwords, I ask them how important each of the dimensions is for evaluating project performance, i.e. which relative weight they attach to each of the dimensions. And the latter is where I would derive the weights from for my overall performance index.

Best regards,

Chris