IBM® SPSS® Amos™ 28

When means and intercepts are not explicit model parameters.

The following lines are equivalent. Either line by itself states that xxx is an exogenous variable and that its variance is unconstrained

xxx
xxx ()

Instead of estimating the variance of xxx, you can set its value to a constant, say a constant 1, as follows.

xxx (1)

You can estimate the variance of xxx while providing a starting value (an initial guess) for the variance estimate. The following line provides a starting value of 55 for the variance of xxx.

xxx (55?)

The following line estimates the variance of xxx and also gives the variance the name "alpha". If there is more than one variances named "alpha" then all of their estimates will be constrained to be equal.

xxx (alpha)

The following line estimates the variance of xxx, gives the variance the name "alpha", and assigns a starting value of 55.

xxx (alpha : 55)

When means and intercepts are explicit model parameters.

The following lines are equivalent. Either line by itself states that xxx is an exogenous variable and that its mean and variance are both unconstrained

xxx
xxx (), ()

You can constrain a variable's mean and/or its variance. The following line sets xxx's mean to a constant 0 and its variance to a constant 1.

xxx (0), (1)

The following line sets the mean of xxx to a constant 0, and also gives its variance the name alpha and a starting value of 55.

xxx (0), (alpha : 55)

When means and intercepts are explicit model parameters, a single variable name must be followed by one of the following.

oTwo pairs of parentheses separated by a comma

oNothing at all

Here are some correct and incorrect examples.

xxx1        {correct}
xxx2 (),()        {correct}
xxx3 (),        {incorrect}
xxx4 (0),        {incorrect}
xxx5 ,(1)        {incorrect}
xxx6 ,        {incorrect}