Working with statistical information means there are a few things you need to be aware of.
Where the data comes from - That is, what organization produced this data, and how did they collect it. Not all surveys, or studies, are created equal. In particular, pay attention to sample size and sampling method. How many people did they count or survey, and how did they decide which people to count or survey?
Margin of error - Most statistical data is not absolutely certain, but contains a margin of error; usually written as +/- (a number). The margin of error indicates that, for the listed number or %age, the real value may be as much or as little more or less as the margin of error. So, for example, if I say 15% of Americans love pecan pie more than life itself, +/- 5%, what I'm really saying is that between 10 and 20% of Americans have this relationship with pecan pie.
Large margins of error suggest imprecise, uncertain statistics, and if the margin of error becomes large enough, the number is not very helpful or informative. It's rare to see margins that large, precisely because saying 30% of Americans are werewolves, +/- 30%, doesn't really mean anything.
Units - Much statistical data is given in small numbers which stand for larger numbers. For example, many population statistics are given in thousands, tens of thousands, or hundreds of thousands of people. Pay attention to these units. When comparing statistics, you must be careful to make sure that you're comparing numbers in the same unit; you can easily trip up and end up comparing one number given in thousands to another number given in hundreds of thousands. Even when not comparing, make sure you understand what the numbers you're looking at really mean. It's a very big difference between 1,100 Americans who own pet leopards, and 110,000 Americans who do. A lot more big cats running around, for one thing.
Great sources of articles, and freely available to the public!
These sources are more focused and less general.
Another place to look for journal articles online.
