This case study was written to reinforce the understanding that a successful hypothesis accounts for all relevant observations and is falsifiable through experimentation. Students evaluate two competing hypotheses to account for the increase in autism spectrum disorder diagnoses. One hypothesis focuses on the correlation between the rise in the rate of diagnosis and an increase in vaccination rates; the other attributes the rise to improved surveillance. Students review the steps of the scientific method and use critical thinking to evaluate different claims and how to determine trustworthy sources. They also consider the controversy surrounding ex-physician and anti-vaccine activist Andrew Wakefield and how fraud and conflict of interest led to the retraction of a paper published in The Lancet. The case is targeted to non-majors college students in introductory science classes, but is also suitable for high school students. It may be used as a starting point for a discussion on the science of vaccination (as an introduction to immunology) or a discussion of scientific fraud.