1. Using Case Studies to Teach Analytical Skills in a Large Lecture
Ann Oliver Cheek
Department of Biology & Biochemistry
University of Houston

2. How I got hooked An opportunity for students to apply knowledge 1999
Literally: a medical case where clinician must consider symptoms, figure out what questions to ask or what lab tests to order, then interpret the additional info to make a diagnosis. I started with case studies in this book in classes of 24 advanced undergraduates in physiology or endocrinology. I divided students into small groups of 3 or 4. I could personally visit all discussion groups .
This book edited by Clyde Herreid of the Natl Ctr for Cas Study Teaching in Science contains many examples and how-to articles about other kinds of case studies.

3. Types of Case Studies Story-telling Discussion Interrupted Case
Directed discussion
Public hearing
Debate or trial
Interrupted Case
Provide background
Ask for hypotheses
Provide author hypothesis
Ask for predictions
Provide data
Ask for analysis
Ask for inference
2013
There are story telling cases illustrated by this prof dressed up as Darwin, discussion cases in several styles, but I will focus on style I’ve used most, the Interuppted Case.

4. Motivation
Make a graph that shows how otter density depends on kelp abundance.
Initial motivation : to teach students how to think. Now I would describe that motivation as a desire to stimulate critical thinking and to teach from experimental data so that students learn how we know what we know.
Motivation to use this approach systematically in large introductory biology lectures came from asking students to do this exercise in class one day about 3 years ago.

5. Make a graph that shows how otter density depends on kelp abundance.
< 50%
Here are some sample answers: fewer than 50% chose to graph this as a line, despite college algebra or its equivalent being a prerequisite for this course.
After this, I began asking my colleagues who teach upper level courses what they wished students knew before they started Genetics or Evolution. Answers: How to read a graph, how to go beyond vomiting key words and apply what they know
Based on my experience with this graphing exercise and on input from my colleagues, I wrote formal objectives for the case studies I was using. This reminds me to develop questions that ask students to practice specific skills over and over.

6. My Objectives for a Case Study
Develop a hypothesis from a research question
Predict results if a hypothesis is true
Distinguish between a hypothesis and a prediction
Decide how to test a hypothesis
Analyze results
Make an inference
Distinguish between a summary of results & an inference
Focus on 3

7. Methods to lead discussion
250 – 500 students
Clicker Only
Hybrid: Paper & Clicker
To make this work in large lecture halls, I use a combination of guiding questions and technology.

8. Skill: Testing a Hypothesis75
More than a Mouthful
by Ann Oliver Cheek
University of Houston

9. Skill: Testing a Hypothesis
student page

10. Decide on the Dependent Variable(s)
The fasted pythons were divided into 10 groups of 4 snakes each. One group of 4 was sacrificed at the end of the fast, Day 0. The remaining snakes were fed a live rat weighing approximately 210 grams. The biologists sacrificed fed snakes 0.25, 0.5, 1, 2, 3, 4, 6, 10, or 15 days after the rat was swallowed. What kinds of data should the biologists collect and how should they do it?

11. Student Answers – 1st use
“They should weigh the stomach and intestines.” “They should weigh the snakes.” This information is presented in the summary of what was already known before the expt.
Problem:

12. What facts are already known about how the python digestive system changes after a meal? Select all that apply.
Digestive and accessory organ size increases.
Stomach acid secretion increases.
Digestive enzyme secretion increases.
Surface area of the intestinal epithelium increases.
Nutrient transport across the intestinal epithelium increases. ✔✔

13. Student Answers – 2nd & 3rd use
“They should … … look at the microvilli.” … weigh the stomach and intestines.” … measure enzyme secretion.” … measure the amount of stomach acid.” … measure HCO3- secretion from the pancreas.”
Some still propose to measure variables for which response is already known
Some propose to measure variables suggested by the MCQ on what’s already known
A few propose something new

14. Vocal cues of ovulation in human females
Skill: Analyze results 75
Vocal cues of ovulation in human females
A Case Study in Reproductive Biology
by Ann Oliver Cheek
University of Houston
Gregory A. Bryant & Martie G. Haselton Biology Letters 5:12-15.

15. Set Up: Authors’ Hypothesis & Prediction
Human females broadcast a detectable ovulatory cue.
The human ovulatory cue is a vocal cue associated with female attractiveness

16. Does pitch differ significantly between high- and low-fertility days of the ovarian cycle?
High fertility
Pitch (Hz)
206 ± 26
211 ± 28*
* p= 0.02, n = 69
Cannot be determined from the data collected.
No. A 5 Hz difference is not detectable to the human ear.
Yes. A woman’s voice is about 5 Hz higher-pitched around the time of ovulation.
Yes. The probability that the difference is due to chance is only 2%.
Select all that apply

17. Skill: Make an inference
These data support the interpretation that men seek out women with high pitched voices because these women are likely to be fertile. ?
Why were nearly 1/3 of students answering that this inference was supported by the data?
Listened to comments when I put this question up on screen – realized students were sticking with their pre-conceived ideas when they answered this question.

18. What kind of unspoken cue do YOU think a woman might give off when she is ovulating?
Visual cue - wears different style of clothing
Visual cue - wears different colors
Olfactory cue - smells different
Behavioral cue - flirts or smiles more
Auditory cue - talks differently
No cue - no external change
Next time I used the case, I gave the background, explained the hypothesis, then asked 2 questions to prod students to examine their pre-conceptions about the topic.

19. Do you think human males can detect when human females ovulate?
No way.
Maybe.
Definitely.

20. These data support the interpretation that men seek out women with high pitched voices because these women are likely to be fertile.
True
False
Answers to the question about whether this inference was supported by the data in the study changed, down from 30% answering TRUE to 18%.
Leads to another question, is there a confirmation bias?

21. Working to Improve Specific Skills
Test a hypothesis …… Begin by asking students to identify what is already known
Analyze results ….. Ask students to identify multiple correct statements of results
Draw an inference ….. Begin by asking students about pre-conceived ideas

22. Questions, Comments, Rotten Tomatoes…

23. How many times during the semester?
I. Energy
Scientific Method Case Study: An end to ulcers?
Digestion
Absorption
Case Study: More than a Mouthful
Cell Membranes
Biomolecules & Cell Structure
Case Study: Miller, 1953
Cellular Respiration
Enzymes
Photosynthesis
III. Animal Homeostasis & Reproduction
Homeostasiss
Homeostasis
Circulation
Neurons
Hormones
Reproduction
Case Study: Vocal cues of ovulation in human females

24. Skill: Predict results if a hypothesis is true
An End to Ulcers?
A Case Study in the Scientific Method by
Kristi Hannam, State University of New York - Geneseo
and
Rod Hagley, University of North Carolina - Wilmington 75

25. Set Up
Provide background on hypothesized causes of human stomach ulcers
Ask students how they would test the “excess acid theory” that excess stomach acid causes ulcers
Suggest a possible study design:
Group 1 given antacids; Group 2 given placebo

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

27. Which graph most closely matches the results you predicted
Which graph most closely matches the results you predicted? (Grp 1 = antacid, Grp 2 = sugar pill)
Group 1 Group 2
Treatment Group
# Ulcers/ patient A C D B

28. Predict the results for pepsin, trypsin, & aminopeptidase-N activity if the authors’ hypothesis is correct.
mmol/min-1
days post-feeding 4 8 12 16
pepsin
trypsin
student page
Students also have a hand-out with this blank graph on it.

29. Which sentence describes the main trend you predicted for trypsin activity?
Trypsin activity will be similar from day 0 through day 15.
Trypsin activity will increase immediately after eating and remain high through day 15.
Trypsin activity will increase initially, then decline to fasting levels by day 15.
Trypsin activity will increase initially, then decline to slightly above fasting levels by day 15.
Rather than collecting student work and grading manually, I follow up with a multiple choice question asking them to choose a description of their graph. I developed these descriptions based on walking around the classroom and looking at student graphs.

30. Set your objectives What skill(s) do you want students to work on?
Are there specific facts you want them to know after the case?

31. Find a published case or write your own
National Center for Case Study Teaching in Science
Primary literature
Featured studies in a textbook
spotlights in Campbell Biology in Focus
A paper you think illustrates the concepts or skills you want students to develop

32. Why bother using a case study?
To train students to read a graph
To kill time because I don’t have enough information to cover
To develop student understanding of experimental design
To develop student ability to evaluate evidence
Because students enjoy being challenged to think.
Responses of UH STEM Faculty

33. Which of these skills are difficult for your students?
Reading a graph.
Identifying appropriate controls.
Making specific predictions from a hypothesis.
Distinguishing between a summary of results and an inference.
None of the above. My students are mature scientific thinkers.