Subject Selection in Clinical Trials

Author: Sarah Kenyon & Charlene Stone

Modifications: Rachel Hughes

Time: 6 class periods

Materials for the experiment:

  • sunscreens with different SPF levels
  • different brand sunscreens with the same SPF levels
  • sunless tanning lotion
  • white and black material
  • plastic wrap and transparencies of different colors
  • glass
  • polarizing and non-polarizing sunglasses
  • lip balms with and without SPF
  • UV light generating lamps (like tanning beds)
  • outdoors access
  • fluorescent lamps
  • incandescent lamps
  • UV color changing frisbees (1 per group)

Make transparencies or photocopies of subjects
Digital camera


Subject descriptions

Designing Experiments

UV Exposure Lab Prep (Power Point Presentation

Does Sunlight Cause Skin Cancer? (pdf format)


In this explain/apply lesson, students will be given the opportunity to design an experiment looking at the ability of different substances to interfere with the transmission of UV rays from different sources. They will then create a question appropriate for a Human Clinical trial based on the results of their experiment. They will complete the lesson by creating a poster that includes a description of their experiment and results, as well as a description of the proposed clinical trial. They will be asked to make decisions as to who should be included and who should be excluded based on inclusion and exclusion criteria that they will construct for a provided subject list. Students will also predict results and describe the implications of these predictions.

Students will:
1) Design and conduct an experiment to test a hypothesis
2) Create a question/objective based on the results of their experiment that can be answered by performing a human clinical trial.
3) Write inclusion and exclusion criteria and apply these criteria to a pool of subjects
4) Predict results of the study and describe implications of the predicted results

National Science Standards
Content Standard A: Scientific Inquiry
Identify questions that guide scientific inquiry
Content Standard E: Science and Technology
Communicate the problem, process, and solution
Content Standard F: Science in Personal and Social Perspectives
Personal and community health
Natural and human-induced hazards
Science and Technology in local, national and global challenges

Teacher Background
As with the previous lesson, it is important to have a good understanding of the nature of Clinical Trials. The following website can provide this information:

http://www.webmd.com/content/pages/13/65814.htm?z=1104_08950_8900_ct_01 Additional information can be found at the Clinical Trials information page.

Does Sunlight Cause Skin Cancer? http://www.ccohs.ca/oshanswers/diseases/skin_cancer.html

Resource Websites

Designing Experiments and Writing Lab Reports http://www.ncsu.edu/labwrite/




1. At the beginning of class remind students of the article, “Does sunlight cause skin cancer?” which they read during one of the stations of the explore lesson, Sun, Skin and Cancer.

2. Elicit from the students the main points covered in the article. Encourage them to point out that there are different types of light, the exposure to which can cause different ill effects to skin. Students should also point out that these negative effects can be prevented in a number of ways- by reducing the amount and type of UV that the skin is exposed to- through materials, sunscreens, and other products.

3. Explain to the students that they should draw upon that reading to develop an investigation where they test the effectiveness of certain products to reduce the effects of UV rays.

Tell them, “First you will design non-human experimental trials to test a question of your choosing, and then design a human clinical trial. At the front of the room there are a number of materials with which you can design your experiment; the only requirement is that you must be testing these materials in response to UV light.” There should be sunscreens of different SPF levels and different sunscreens with the same SPF level as well as sunless tanning lotions, white and black material, plastic wrap and glass, polarizing and non-polarizing sunglasses, plus lip balms with and without SPF. There will be UV-light generating lamps, as well as access to the outdoors and fluorescent and incandescent lamps. UV reactive Frisbees will be used as indicators of UV blocking.

4. Students will (in groups) use the Designing an Experiement and Writing a Hypothesis handout to record their question, their prediction and hypothesis as well as a method or protocol for their experiment.

5. On the second day, students will conduct their experiment. When they have completed the experiment they will write their results. It would be useful to have a digital camera on hand to take pictures, as the results are likely to be qualitatively visual.

6. As they finish, have students clean up their areas and brainstorm, as a group, on any questions that their experiment raised that could be answered with human trials. Have them, as a group, identify one of these research questions that they might like to address and what the objective of this study will be. (i.e. “We want to address whether brand name sunscreen A (SPF 15) works as well as generic sunscreen B (SPF 15) at blocking the effects of UV rays from the sun on human skin, with the objective to see effectiveness versus price”).

Subject selection (day 3):

7. Ask the class “What are some reasons why some people should be excluded from a study? Are there certain people who are riskier to have in a study than others? Why? How homogeneous should your study group be? Does this depend on your question? How does the homogeneity of your study group affect the study size? What reasons are there to limit the number of subjects in your study? What reasons are there to increase the number of subjects?”

8. When the class has considered these questions, have them individually come up with a list of exclusion and inclusion criteria for their particular study.

9. Then have each research group get together and pool their ideas and write a common inclusion and a common exclusion criteria for their study.

10. Each group will then receive a handout with a list of potential subjects, and they will choose appropriate subjects for their study (indicated by a check next to the included subjects) and a reason why each excluded patient was excluded, based on their exclusion criteria.

11. Each group will then identify (if desired) additional criteria for exclusion that they may have identified by assessing the provided subjects.

12. Then tell students that for their clinical trial, they MUST have 14 subjects from this list. If they have more, who do they now exclude? If they have fewer, who do they now include?

13. Ask the class to generate a list of exclusion criteria (you will only do this for now (??))- taking note on the board of when there are ones common to multiple groups.

14. Then ask the class: “Which groups had not excluded enough subjects? What did you use as extra criteria for exclusion? Which groups had excluded too many? What criteria did you use to include some subjects you had already excluded? What might these decisions mean for your results? Do you feel what you did was appropriate? If not, what would you, if you were a researcher in this position, do differently?”

Treatment selection (day 4):

15. Now that students have their included subjects, they will be asked to divide them into their treatment groups. Each research group should identify the treatment groups they have and how they are assigning subjects to each treatment. They should identify, in writing, how the way they assigned treatments will achieve their stated research objective. (random vs. matched)

Poster creation (days 4-6):

16. Student research groups will then be responsible for creating a “Human Clinical Trial” addition to their poster. These posters must include:
a. Results from their pre-clinical experiment
b. Clinical proposal (research question, objective, rationale and treatments)
c. Inclusion criteria
d. Exclusion criteria
e. Predictions

17. Posters should be ~60% from a, with the remaining 40% from b-e.

Museum Walk (day 6):

18. Students will place posters around the room and take turns standing by their poster as the other students in the group rotate through the other posters.

Have students respond to the following in their science notebook: “In what way do our lessons on the physiology of skin, our survey of recent research of skin cancer issues and our creation of a clinical trial address Environmental Health?” Have them also write their own definition of “Environmental Health”. Discuss their answers as a class.

Throughout the week, students will work on their questions, methods, and poster presentation both in class and at home.

Embedded Assessment
Through their group topics, teachers can assess their ability to work together to generate questions based on their current knowledge. Their ability to visually represent their experiment and Clinical trial proposal, presentation skills, as well as the ability to listen and respond or appropriately question new material can be assessed during the Museum walk. In their final responses to the provided statement or question, they will be assessed as to their ability to integrate the information in the lessons in this learning cycle and describe it in relationship to the larger concept of Environmental Health.


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

1996-2007, The University of Arizona
Last update: November 10, 2009
  Page Content: Rachel Hughes
Web Master: Travis Biazo