I'm assuming you are trying to install version 7.0.1426.
To skip installation of Google Chrome, choose 'Custom Install' instead of the default one. In Custom Install is an option to untick the install there. Avast! has this set to "opt-out" rather that "opt-in" because they believe Chrome is a safer browser to use than other browsers. So users are faced with a possible unwanted install of Chrome.
So the default setting is to automatically install Chrome for the user.
You don't want that, so untick the box to install (opt-out) Chrome. Clearing this box will stop the Chrome install. You should not see Chrome when installation is done.