Nada Rabie, formative latent variables are formed by indicators that are not necessarily highly or not correlated at all (e.g., socioeconomic status) whereas reflective latent variables are reflected by indicators that are expected to be highly correlated (e.g., job satisfaction).

Hi @Nada Rabie

Amos works using the maximum likelihood method, that is, it analyzes the covariance-based structural equation model. Here, in order to analyze the formative and reflective measurement models mixed, it is necessary to specify the model well. But PLS-SEM is a variance-based method. A drawback of the PLS-SEM technique is the absence of goodness-of-fit indices, but PLS also has its own measurement criteria. The main difference between CB-SEM and PLS-SEM;

CB-SEM is a confirmatory method

PLS-SEM is an exploratory method.

Best,

I suggest you watch the videos of Prof. Game Gaskin for a better understanding.

https://www.youtube.com/user/Gaskination

The formative construct is an index or composite, removing an item may lead to a wrongful measurement of the whole as each item adds to the overall index (i.e. it forms the whole construct) e.g. for calculating BMI (Body Mass Index), you need both the height and the weight of a person, take out one and you cant calculate BMI.

On the other hand, a reflective construct is one in which removing an item or two will not affect the overall construct as each item is a reflection of the construct i.e. each item essentially points towards the same idea.