1. A Case Study in the Scientific Method
An End to Ulcers?
A Case Study in the Scientific Method

2. History of the understanding of stomach function & ailments
HIPPOCRATES
WILLIAM BEAUMONT

3. Q1: What do you think causes ulcers?
A: Stress. B: Excessive stomach acids. C: Bacteria. D: A bad diet and alcohol use. E: Being overweight.

4. What Causes Ulcers?
Design an experiment to test if your hypothesis is true.
In your group, design the experiment. Remember, be specific about how you would treat your groups and what you would measure!

5. Q2: Which is a good way to test the “excess acid hypothesis”?
A: Examine ulcer patients of a range of ages and measure their stomach acid levels. B: Have volunteers drink alcohol and measure their stomach acid levels. C: Lower stomach acid levels of some volunteers (using drugs/antacids), and measure numbers of ulcers in all volunteers. D: Put volunteers through a stress test and then measure their stomach acid levels.

6. Q3: What step in the scientific method does this test represent?
A: Making observations. B: Developing a hypothesis. C: Testing a hypothesis. D: Getting results.

7. A Possible Study Design
Doctors divide patients into two groups:
After 3 months, the number of ulcers per patient is checked.
Predict what the results would look like if the excess acid theory was supported.
Group 1 received antacids and were instructed to take them 3x/day
Group 2 received sugar pills and were instructed to take them 3x/day

8. # Ulcers/ patient Group 1 Group 2 Treatment Group
Draw this graph: Predict what the results would look like if the “excess acid theory” was supported by the results of this study:
# Ulcers/ patient
Group 1 Group 2
Treatment Group

9. Q4: Which graph most closely matches the results you predicted?B
# Ulcers/ patient
# Ulcers/ patient
Group 1 Group 2
Treatment Group
Group 1 Group 2
Treatment Group D C
# Ulcers/ patient
# Ulcers/ patient
Group 1 Group 2
Treatment Group
Group 1 Group 2
Treatment Group

10. Patients who took antacids had decreased ulcer symptoms.
If the patients stopped taking the antacids their ulcers returned.
Image by: Midnightcomm

11. Dr. J. Robin Warren: (pathologist)
Examines stomach biopsies of patients with various stomach ailments.
Low Power

12. Dr. Warren thought he saw:
High Power
Helicobacter pylori (a new species of bacteria)
But no one else believed him!
The black squiggly spots on the slide
are bacteria that Dr. Warren observed
In his biopsy slides.

13. Q6: Dr. Warren’s colleagues did not believe there were bacteria in the stomach. Why do you think other pathologists did not believe bacteria were in the stomach biopsies?
A: Bacteria are never found inside the human body. B: The pH of the stomach is too acidic for any bacteria to survive. C: No one else had reported seeing bacteria in their biopsy samples. D: Ulcers and stomach cancer are caused by age, stress and diet – bacteria have nothing to do with the problems the patients came to the hospital for.

14. Talk to your neighbor Dr. Warren thinks H. pylori causes ulcers.
What is another hypothesis to explain why Dr. Warren was finding bacteria on his slides? (there are at least three alternative hypotheses...)

15. Alternative explanations (hypotheses):
1. The biopsy specimens were contaminated AFTER samples were taken from the patients.
2. The bacteria live in the stomach, but do no damage.
3. The slides were already contaminated with bacteria.

16. Dr. Barry J. Marshall Joins Dr. Warren’s Research
Hypothesis: Bacteria cause stomach ulcers.
If you were working with Drs. Warren & Marshall to design a study to determine whether the bacteria caused ulcers, how would you do it?

17. Their First Survey Study:
100 stomach ulcer patients surveyed (biopsy taken).
100% had H. pylori present.

18. Q7: The doctors treated ulcer patients with antibiotics to see if the disease stopped. What is missing from their study?
A: An experimental treatment. B: A control group. C: An independent variable. D: A dependent variable. E: A hypothesis.

19. Important Aspects of Experimental Design
Testable hypothesis, i.e., a way to measure a response and a way to divide groups up into:
Control and Treatment Groups
Control is group that does not get the hypothesized treatment.
Treatment is group that does get the hypothesized treatment.

20. The Importance of Controls
Why do we need controls? Explain to your neighbor …

21. If they set up their antibiotic study with a treatment group receiving antibiotics and a control group receiving a placebo (no antibiotics), what results would you expect if the original “excess acid hypothesis” was supported?
Control Experimental
Number of ulcers
after 2 months

22. Q8: What results would you expect if the old “excess acid hypothesis” were supported?B A
Number of ulcers
after 2 months
Number of ulcers
after 2 months
Con Exptl
Con Exptl D C
Number of ulcers
after 2 months
Number of ulcers
after 2 months
Con Exptl
Con Exptl

23. What results would you expect if Drs
What results would you expect if Drs. Warren and Marshall’s “bacteria cause ulcers” hypothesis is supported?
Control Experimental
Number of ulcers
after 2 months

24. Q9: What results would you expect if the old “bacteria cause ulcers hypothesis” were supported?
Number of ulcers
after 2 months
Number of ulcers
after 2 months
Con Exptl
Con Exptl C D A
Number of ulcers
after 2 months
Number of ulcers
after 2 months
Con Exptl
Con Exptl

25. Actual Results of Warren & Marshall’s Study
When treated with antibiotics, 80% of patients were permanently cured of their ulcers.
To further demonstrate the cause and effect relationship, Dr. Marshall (who did NOT suffer from ulcers), swallowed a flask of H. pylori from the lab.
Within a week he was suffering from symptoms of gastritis and had H. pylori populations in his stomach!
He cured himself with an antibiotic treatment.

26. Q12: If your family member was diagnosed with stomach ulcers, what do you think the recommended treatment would be?
A: Lower stress levels. B: Change diet to eliminate spicy food. C: Take a course of antibiotics. D: Drink milk to lower stomach acid levels. E: Lose weight and exercise.