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PDF Files for PrintingActivity 4 - Evaluating Claims About Cancer

At a Glance

newspaper headline: product causes cancerFocus: Students identify claims about UV exposure presented in a selection of media items, then design, execute, and report the results of an experiment designed to test one such claim.

Major Concepts: Scientists use systematic and rigorous criteria to evaluate claims about factors associated with cancer. Consumers can evaluate such claims by applying criteria related to the source, certainty, and reasonableness of the supporting information.

Objectives: After completing this activity, students will

Prerequisite Knowledge: Students should have sufficient understanding of the methods of science to develop a hypothesis, design an experiment to test that hypothesis, and draw reasonable conclusions from the results.

Basic Science-Public Health Connection: This activity provides the opportunity for students to discover how science can help individuals and society evaluate claims about cancer.

Introduction

Although most of your students will never acquire or need a detailed understanding of the biology of cancer, all of them will need to understand and evaluate claims about cancer that they encounter in casual conversation, in media items, and even in reports from health care workers. Some of these claims may be vague, either in substance or in origin. Some may be exciting and seem to offer great hope. Others may be alarming. In some cases, these claims may conflict.

How do scientists evaluate claims about cancer? And how can your students, as scientifically literate citizens, evaluate such claims, both for their own satisfaction and as a solid foundation for thinking about and voting on policy issues?

In this activity, students examine several media items about exposure to the sun and the development of skin cancer and work in teams to identify the claims that each media item makes. Students are challenged to describe ways that scientists might evaluate these claims, and then are introduced to a model system involving yeast sensitive to UV (ultraviolet) light that they can use to test aspects of these claims. Each team designs, executes, and presents the results of a controlled experiment testing one of these aspects. The activity ends with a class discussion of (1) how scientists evaluate claims about cancer and (2) the criteria that nonscientists can use to evaluate such claims.

Materials and Preparation

You will need to prepare materials in advance for the laboratory exercise. Ordering information and preparation directions are immediately following the activity.

You will need to prepare the following additional materials before conducting this activity:

*You will need one Media Item handout for each student in your class. Note that every student in one team gets the same handout, but different teams get different handouts.

Procedure

DAY 1

1. Ask students to organize into teams. Distribute the masters so that each team has a different master; each member of a particular team should have the same master.

2. Direct students to read their media items, then work together to identify the major claims that their assigned item makes about the product, ultraviolet (UV) light, and cancer. Ask students also to describe the evidence on which these claims seem to be based.

Give the teams about 5 minutes for this discussion.

3. Conduct a brief class discussion about the media items by asking the following questions:

Students should not find it difficult to identify these claims. Possible answers include the following:

The media items do not provide any evidence to support these claims.

Students likely have heard many claims. Allow them to list not only outlandish claims that they may have heard in the media, but also more reasonable claims that they may have heard from parents, friends, and even reputable magazines and health care professionals. Technically, any information that we hear or read about cancer is a "claim" that someone is making.

Students should already understand that scientists evaluate such claims through rigorous experimentation, the requirement of evidence to support a claim, careful review by other scientists of procedures and conclusions, and the requirement that results be replicable. Look for these and similar answers from your students; if they are not forthcoming, ask probing questions such as, "Is it sufficient for a scientist to make a claim without providing evidence to back it up?" and "If certain results can be obtained only by one scientist working in a particular laboratory, what would you think of claims based on these results?"

mobius stripStudents have the opportunity here to experience how scientific experiments can lead to reasonable claims about how individuals can help prevent skin cancer. Point out that basic experiments, such as the one they are about to conduct, have led to a variety of actions on behalf of public health, including the banning of certain food additives and warnings they see on consumer products.

4. Explain that in this activity, students will have an opportunity to test claims that are similar to those they encountered in their media items and will learn questions that citizens can ask about claims they hear in the popular press and from other sources.

5. Distribute one copy of Master 4.5, Using a Model System to Test Claims About UV Light, to each student. Ask students to work in their teams to design and conduct a controlled experiment that tests a claim related to their media item.

You may wish to explain that often scientists use model systems to evaluate certain claims that would not be appropriate to test using people as subjects. Often, these model systems involve other species. In this activity, students will use yeast as their model system.

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