What does it mean when a news story or commercial says that four out of five people agree on something? How do these ratios work in real life? Would you get the same numbers if you asked the people you know?
When you see something that reports on a ratio of people, it's usually referring to the results of a very large survey. A 2011 poll by Gallup, for instance, found that 9 out of 10 Americans believe in some sort of a deity. However, the 9:10 ratio only applied to the "group" of all Americans. When the survey results were analyzed by geographic area or age groups, the answers varied.
This is also the case with other broad surveys. For example, another study conducted in 2012 found that 3 out of 5 U.S. teachers have children in class who come to school hungry. Does this mean that if you interview 5 teachers at your school, exactly 3 of them will teach kids who come to school hungry? Probably not. Some schools have many students who lack food at home, while other schools have very few students who go hungry. Depending on your school, you might find that 5 out of 5 teachers have hungry students, or that 0 out of 5 teachers have hungry students. The results of nationwide surveys do not necessarily reflect statistics at the local level.
So what are these ratios good for? They are a quick way to see how popular an idea is or how common a problem is across the country. They enable us to see general, nationwide trends. Over time, we can see how America is changing. For instance, almost no Americans supported gay marriage in the 1950s. In 2013, more than 5 out of 10 do.
See for yourself: http://www.today.com/video/today/52305482
Check out the following articles to read about more ratios that made the news.