Norman and Walter agree! The living wage is determined based on the hourly rate an individual, as sole provider, must make to support his or her family. If you are not sure why a living wage is important, take a look at this post from the Economic Justice Coalition.
You can visit the Living Wage Calculator to see how cost of living in your area compares with the minimum wage. In Ithaca, the living wage is $8.88 while the minimum wage is $7.25. In Ardmore, people making minimum wage fair better: a living wage there is only $7.14. People in large cities, as you would expect, are in the worst positions. The living wage in New York City is $11.86, in San Francisco, it's $12.65, and in San Diego, it's $11.68. In Ithaca, a local organization, the Tompkins County Worker's Center, among many other programs, certifies businesses who pay a living wage.
Here's an interesting lesson plan for high school students from PBS in association with the film Waging a Living. It has a segment related to the film, but the activity on calculating a living wage can be used independently.