To demonstrate how descriptive epidemiological clues can be used to make educated guesses as to what might be the cause of a disease.
This lesson is part of a 34-lesson curriculum called Detectives in the Classroom, a project of the College of Education and Human Services at Montclair State University. The project is supported by Science Education Partnership Awards from the National Center for Research Resources, National Institutes of Health. The entire curriculum, which can be viewed at the Detectives in the Classroom site, consists of five instructional modules that explore specific health-related issues relevant to middle-school students through the science of epidemiology.
This lesson is the third of six lessons in Module 1 that all deal with the Essential Question: “Why do some people get sick while others remain healthy?” In learning to answer this question, students will come to appreciate the Enduring Understanding that “Clues for formulating hypotheses can be found by describing the way a disease is distributed in a population of people in terms of person, place, and time.” The lessons which precede and follow this lesson help develop this Essential Understanding but are not prerequisites.
Children are curious about things from birth. Curiosity does not have to be taught. The problem is the reverse: how to avoid squelching curiosity while helping students focus it productively. By fostering student curiosity about scientific, mathematical, and technological phenomena, teachers can reinforce the trait of curiosity generally and show that there are ways to go about finding answers to questions about how the world works. Students will gradually come to see that some ways of satisfying one's curiosity are better than others and that finding good answers and solutions is as much fun as raising good questions.
Balancing open-mindedness with skepticism may be difficult for students. These two virtues pull in opposite directions. Even in science itself, there is tension between an openness to new theories and an unwillingness to discard current ones. As students come up with explanations for what they observe or wonder about, teachers should insist that other students pay serious attention to them. (Benchmarks for Science Literacy, p. 284.)
This lesson will help students understand that hypotheses are valuable, even if they turn out not to be true, if they lead to fruitful investigations. The lesson also will help students understand that often different explanations can be given for the same evidence, though it is not always possible to tell which one is correct.
You are encouraged to read through the Epidemiology Background sheet to prepare for this lesson.
Before you start this lesson, you should cut out the List of Possible Exposures cards and number them on the back side.
Students already should be familiar with the basic concepts and terminology of Epidemiology. These can be reviewed by asking these questions:
- What is descriptive epidemiology? (It describes how a disease is distributed in a population of people.)
- What are the three main categories of descriptive epidemiological clues? (They are person [who], place [where], and time [when].)
- What is a hypothesis? (It is an educated guess.)
- What is the relationship between descriptive epidemiology and hypotheses? (Descriptive epidemiological clues provide evidence for formulating hypotheses.)
Continue with a specific example:
- What might be the descriptive epidemiology of a disease if it were caused by WHISTLES?
- Write suggestions on the board as to who might be likely to get the disease—e.g., lifeguards, referees, policemen.
- Write suggestions on the board as to where the disease would be most likely to occur—e.g., pools, gymnasiums, sporting events.
- Write suggestions on the board as to when the disease would be most likely to occur—e.g., hot days, school days, summer.
Then ask students to imagine someone who does not know that WHISTLES caused this disease and is looking at these clues and is trying to make an educated guess as to what caused the disease. That student is trying to answer the question, “What’s my hypothesis?”
Tell students that generating hypotheses is one of the skills of epidemiologists, disease detectives. They are able to look at descriptive epidemiological clues and formulate hypotheses or educated guesses that might explain:
- Why some people became sick and others did not,
- Why the sickness occurred in some places and not in others, and
- Why the sickness occurred at some times and not at others.
Continue this lesson by informing students that they will perform an activity that will help them learn how person, place, and time (PPT) clues are used to form hypotheses. By the end of the lesson, they should be able to formulate logical and alternative hypotheses, formulate arguments that show the uncertainty of these hypotheses, and thereby describe disease distribution logically.
Give each student a copy of the Epi Log Worksheet: PPT Sheet. Then provide each student with a different index card, each with a hypothesized cause of a disease written on it. Be sure to tell students to leave the index card face down on their desks and to look at it without anyone else seeing it. Emphasize these points:
- Do not show anyone what is written on the index card.
- Do not tell anyone what is written on the index card.
- Do not ask others what is written on their index cards.
Ask students to note the number written on the index card and write that number on the lower right corner of their worksheet. Then ask students to fill in the “who,” “where,” and “when” descriptions, just as they had done with the WHISTLES disease.
Once each student has filled out his/her worksheet, divide the class into Epi Teams of 4-5 students each. Then give each student the Epi Log Worksheet: Hypothesis Chart. The students will then fill out their Hypothesis Charts based on information from the other members of their Epi team's PPT sheets.
This is accomplished by following the steps described in the What's My Hypothesis? book, pages 13-23.
Conclude the lesson by telling students that in the real world no one has the cause of a disease written on a card. Epidemiologists know that some people get sick, in some places, some of the time. This is a fundamental epidemiological skill: the ability to look at how a disease is distributed in a population, in terms of person, place, and time, and make educated guesses.
Assess student understanding by their participation in the class discussion and their contribution to their Epi team.
This lesson is one in a series of 34 lessons (investigations) that comprise the Detectives in the Classroom epidemiological curriculum for middle-school students. All of the lessons may be viewed on the Detectives in the Classroom site.
You can extend the ideas in this lesson with another Science NetLinks lesson called Collapse 2: Interpreting the Evidence, which addresses issues of values and attitudes, particularly the importance of honest, clear, and accurate record keeping; and the fact that different explanations can be given for the same evidence.