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Lesson 3: Scientific Method
Estimated Time: 15 minutes
Small
Group
Activity
Divide the students into
groups of 3 or 4. Give the groups a copy of the scientific method.
Using the scientific method below have the groups outline a plan to find the cause of
these birth defects. Then have group members discuss their plans
with the class.
Steps of the scientific method
1. Name the problem or question
2. Form an educated guess (hypothesis) of the cause of the problem and make
predictions based upon the hypothesis
3. Test your hypothesis by doing an experiment or study (with proper
controls)
4. Check and interpret your results
5. Report your results to the scientific community
Epidemiologists use different types of studies. One type is observational.
This type watches people over a certain amount of time to see of their health habits or traits
relate to whether or not they get certain diseases. The researcher does not change a person's habits or
give them any treatments. They watch to see what people do and determine
whether or not they get
a disease. There are two types of observational studies: prospective and
retrospective. A prospective study looks at the
characteristics of a group of people and then follows them to see who gets a
disease and who doesn't. This can take a while. If we found 100 young women and
found out about some of their lifestyle and genetic characteristics, and then followed them for five years to see which ones have
babies with birth defects it would be an observational, prospective study.
A retrospective study looks at the people who have the disease
or health problem and tries to determine what characteristics they have
that may have contributed to them getting the disease. For example, if we found 100
women who had babies with a birth defect and asked them questions about the
types of food they ate, or where they worked,
this would be an example of a retrospective study.
A case-control study is a type of retrospective study. Epidemiologists use the information that they have collected to guess (form a
hypothesis) about what caused the health problem. Then they try to determine
who has the health problem or disease, and who does not. A case is
the occurrence of the health problem or disease in a person. A control
is the absence of the health problem or disease in a person.
Researchers compare the
cases and controls by talking to the people who
have the health problem or disease as well as the people who do not have
the health problem or disease to see what is different between them.
After an observational study suggests what may be the
cause of the health problem or disease and how they plan to treat it, then
researchers do another type of study. This is a testing (experimental)
study. One group of people is given something to take (exposed group), and another
group is not given that substance (non-exposed group). Then the scientists see if
the group that received the substance has different results than the group that did not
receive the substance.
When doing a study, scientists must follow certain rules to treat people fairly:
1) The first principle of medicine is to DO NO HARM!
Scientists must not test something on people that is already known to be harmful.
2) If a treatment is proven helpful, the study must be
stopped and the treatment must be offered to everyone who could be helped by it.
3) If during the study the results begin to show harm, the study
must be stopped.
For example, many studies have already shown that smoking and alcohol can hurt babies
before they are born. Since this is known, it would be wrong for a study to ask
pregnant women to smoke or drink alcohol to see how their babies turn out.
Teachers: Link for a larger
copy of this chart.
Epidemiologists begin studies with a complete version of the scientific method.
Below are the 10 steps they use to conduct an investigation. In real life, several
steps may be done at the same time, or in a different order.
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1. Prepare for field work |
6. Make hypotheses |
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2. Show that an outbreak exists |
7. Test hypotheses |
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3. Confirm the diagnosis |
8. Refine hypotheses and carry out more studies |
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4. Define and find cases |
9. Begin control and prevention
measures |
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5. Describe and line up the data in terms
of person, place, and time |
10. Share findings |
Next, we will look at the methods used by epidemiologists to learn about
the cause of the cluster of birth defects in the Texas babies.
Link to Lesson 4:
Scientific Investigation
Date: September 6, 2006
Content source: National Center on Birth Defects and Developmental
Disabilities
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