Numbers are powerful. Words can sometimes be difficult to define, and are therefore ambiguous, but numbers and statistics tend to provide a feeling of solidity and security. 5 is always greater than 4, and 10 is always half of 20.
As sure as numbers can be, statistics can be confusing, and easily misunderstood or misused. Even when used correctly some writers and presenters make the mistake of assuming that the statistics speak for themselves. A statistic is a measurement of something, and in order for an audience to understand the statistic they need to be aware of exactly what was measured, how it was measured, and how that information was reported.
The Writing Center at UNC-Chapel Hill has an excellent online handout about understanding the using statistics effectively.