Which of the following experiments could test the hypothesis that bacteria cause ulcers in humans? (Assume each experiment includes a control group.) Explain what evidence would be provided by the results of the experiment. a. Identify the microbes found in the stomachs of ulcer patients. b. Treat a group of ulcer patients with antibiotics. c. Place a group of ulcer patients on a strict low-acid diet. d. Obtain stomach fluid from ulcer patents and feed it to mice.

Verified step by step guidance

1. Identify the hypothesis: The hypothesis states that bacteria cause ulcers in humans. The experiment chosen should directly test the presence and effect of bacteria in causing ulcers.
2. Evaluate option a: Identifying microbes in the stomachs of ulcer patients would show what types of bacteria are present but does not directly test if these bacteria cause the ulcers.
3. Evaluate option b: Treating ulcer patients with antibiotics targets the bacteria specifically. If the ulcers heal following antibiotic treatment, this suggests that bacteria were causing the ulcers, providing direct evidence supporting the hypothesis.
4. Evaluate option c: Placing ulcer patients on a low-acid diet addresses the stomach environment rather than the bacteria directly. Improvement in this scenario could suggest that acid, not bacteria, is the primary cause of ulcers.
5. Evaluate option d: Feeding stomach fluid from ulcer patients to mice and observing if they develop ulcers could indicate if something in the fluid (like bacteria) causes ulcers. However, this method also includes other factors present in the stomach fluid, not isolating bacteria as the sole variable.

Key Concepts

Hypothesis Testing

Hypothesis testing is a fundamental scientific method used to determine the validity of a proposed explanation for a phenomenon. In this context, it involves designing experiments to test whether bacteria are the causative agents of ulcers. Each experiment must include a control group to compare results and establish causation rather than mere correlation.

Control Group

A control group is a baseline group in an experiment that does not receive the treatment or intervention being tested. It serves as a comparison to the experimental group, allowing researchers to isolate the effects of the treatment. In the context of testing the hypothesis about bacteria and ulcers, the control group helps determine if observed effects are due to the bacteria or other factors.

Causation vs. Correlation

Causation refers to a direct cause-and-effect relationship between two variables, while correlation indicates a relationship where two variables change together but do not necessarily influence each other. Understanding this distinction is crucial when interpreting the results of experiments testing the hypothesis that bacteria cause ulcers, as it helps clarify whether the presence of bacteria is a cause of ulcers or merely associated with them.