What is the difference between formative and reflective measurement models?

Can anyone provide examples as to why choose one over the other? Are they calculated diferently?

Answer

Yes, they are very different.

Conceptually, a reflective measurement model happens when the indicators of a construct are considered to be caused by that construct. For example, an intelligence test: if you are more intelligent, you have a higher probability of getting the correct answer to a question. Hence your intelligence level is (theorized to) predict the score on the question. The latent variable (intelligence) is the predictor, the measured variable (test) is the outcome.

A formative measurement model happens when the measured variables are considered to be the cause of the latent variable. The value of a car is determined by its age, condition, size, make, etc. If a car is more valuable it does not turn from a Mercedes into a Ford. Instead, being a Mercedes is a predictor of being more valuable, and value is the outcome.

In a reflective measurement model, we expect the covariances between the indicators to be zero, when the latent variable is partialled out – that is the reason that two test scores correlate is because they are caused by the same thing.

In a formative measurement model, we don’t have anything to say about the covariances of the items, they could be zero, positive or negative. Formative measurement models are harder to estimate – they are not identified on their own.

Attribution
Source : Link , Question Author : lf_araujo , Answer Author : Jeremy Miles

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