From what I see, this is based on median income for those working.  And not taking into account employment rate, for example.  Or cost of living.   Which the article does list for each state discussed.

Richest

5.Connecticut: 67,000

4.Hawaii: 68,020

3.New Jersey: 70,165

2.Alaska 72,237

1.Maryland 72,483


http://money.msn.com/investing/americas-richest-and-poorest-states-1

The United States added more than 2.3 million jobs in 2013, the most in any year since 2005. Despite this, income levels and poverty rates did not improve in most of the United States last year, according to recently released figures from the Census Bureau's American Community Survey.

While many American households continue to struggle to make ends meet, those in the richest states continued to earn far more than households in the poorest states. The wealthiest state in the U.S. last year boasted a median income of $72,483, compared to a median income of just $37,963 in America's poorest state.

One of the most important determinants of income is employment, because most Americans rely on their jobs as their largest source of income. Several states with high incomes also had low unemployment rates.