This document provides an example case study from a biology class (BIOL 310) on ulcers. The case study follows the scientific process as doctors tested the hypothesis that excess stomach acid causes ulcers. It describes how doctors originally believed this, but later studies using controls and treating groups with antibiotics supported the hypothesis that bacteria (Helicobacter pylori) actually causes ulcers. The document provides details of the relevant studies, individuals involved like Drs. Warren and Marshall who discovered H. pylori, and how their work revolutionized ulcer treatment and our understanding of links between infection and disease.