The (mis)use of statistics

People (especially journalists) don't know that much about statistics. So we should beware of people that may want to mislead us using the art (or science if you will) of statistics. Statistics isn't anything but putting together a bunch of data and analysing it (using regressions -in the case of social sciences, particularly Economics, this is called Econometrics-, descriptive statistics, and a long etc.) Nonetheless, we should be very careful when dealing with real life data. Some of the usual fallacies commited by people that are not familiar with statistics include the following:

-Usually people think correlation implies causality. This is a big mistake. The fact that two variables are correlated does not mean one causes another. I'll make it clear with an example, once, I had a professor that showed us that Presidential approval and the sale of new automobiles in Mexico was highly correlated. Does this mean one causes the other? Not at all, both are probably caused by the performance of the economy.

- Quantity. When the A/H1N1 virus hit Mexico, people said its effects were harsher on the young (who are usually more prepared againt this type of disease). More young adults died than any other age group. Why? Young adults are the largest age group in Mexico. They were bound to have more dead if the death rate was uniformly distibuted among the population.