Does a positive test mean that you have a disease? Does a negative test mean you're healthy? Unfortunately, the answer to both these questions isn't a definitive "yes". How good a test is depends on it's sensitivity and specificity. Learn about both, and why understanding these test characteristics is so important. Next week we'll talk about what this all means in part II of this series, The Bayes Theorem. The Vermont Study: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3611728/ John Green -- Executive Producer Stan Muller -- Director, Producer Aaron Carroll -- Writer Mark Olsen - Graphics http://www.twitter.com/aaronecarroll http://www.twitter.com/crashcoursestan http://www.twitter.com/realjohngreen http://www.twitter.com/olsenvideo