Hello

We have the following sample space:$\displaystyle \Omega = \left\{{1,2,3}\right\}$

Is the following event of $\displaystyle \Omega$ a sigma-algebra?

$\displaystyle

A = \left\{{\left\{{\emptyset}\right\},\left\{{1,2,3}\ right\},\left\{{1}\right\},\left\{{2}\right\},\lef t\{{1,3}\right\},\left\{{2,3}\right\}}\right\}

$

I think the union property is not satisfied. Right?

Thanks