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#### Monamandala

##### New member

- Jan 9, 2020

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$Hessian = \frac{\partial^2 f}{\partial x_i \partial x_j}$

However, I have come across a different expression, source: https://users.ugent.be/~yrosseel/lavaan/lavaan2.pdf (slide 40)

$nCov(\hat\theta) =A^{-1}=[-Hessian]^{-1} = [-\partial F(\hat\theta)/(\partial\hat\theta\partial\hat\theta')]^{-1}$

A - represents a hessian matrix.

I am curious are the one attached and usual hessian matrix interchangeable somehow? Why is there no square and a derivative appears in the denominator in the attached example?