Naked Truth Investing: Would you go to a heart doctor who couldn't identify the aortic valve?

This is part of a new series of columns called "The Naked Truth," by retirement expert Dan Solin. Please bring him your questions, in the comments box, and he will answer as many as he can.

I am sure you wouldn't entrust your health to a medical professional who didn't have a complete knowledge of her area of expertise.

Yet millions of investors rely on "investment professionals" who can't define risk, much less measure it. If you don't know the risk of your portfolio, you can't invest intelligently for retirement.