It's a common belief that if someone has a medical condition, a patient can take a treatment and the condition gets better or goes away. That is, improvement is directly related to intake. However, as it turns out, there's often a good chance the patient would have gotten better without the treatment. There's also a chance a treatment does nothing.
Austin Frakt and Aaron E. Carroll for the Upshot describe these chances through a metric called number needed to treat, or N.N.T. The simple animations throughout the article provide a great dose of perspective to the odds.