Replication in Science
Jean Brainard, Ph.D.
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Printed: August 20, 2013
AUTHOR
Jean Brainard, Ph.D.
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C ONCEPT
Concept 1. Replication in Science
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Replication in Science
• Define replication.
• Explain the importance of replication in science.
Did a math teacher ever tell you to check your work? If you’re adding numbers, that means repeating the calculation
to see if you get the same answer the second time. If you get the same result twice, then the answer is probably
correct. But if you get a different answer the second time, at least one of the results must be incorrect. Then you
have to add the numbers a third time and hope that the third answer will agree with one of the other two.
Replication
Scientists also have to “check their work.” The results of an investigation are not likely to be well accepted unless
the investigation is repeated—usually many times—and the same result is always obtained. Getting the same result
when an experiment is repeated is called replication. If research results can be replicated, it means they are more
likely to be correct. Repeated replication of investigations may turn a hypothesis into a theory. On the other hand, if
results cannot be replicated they are likely to be incorrect.
Why Replication Is Important in Science: An Example
The following example shows why replication is important in science. In 1998, a British researcher published an
article in a medical journal reporting that he had found a link between a common childhood vaccine and autism
(see Figure 1.1). According to the article, children in his study developed autism soon after receiving the vaccine.
Following publication of the article, many parents refused to have their children vaccinated. Several epidemics
occurred as a result, and some children died of the diseases.
Soon after the original study was published, other researchers tried to replicate the research. However, it could not
be replicated. No other studies could find a link between the vaccine and autism. As a result, scientists became
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FIGURE 1.1
This child is receiving an MMR vaccine,
the childhood vaccine that was linked with
autism in a 1998 article.
MMR pro-
tects children from three different infectious diseases: measles, mumps, and
rubella. These diseases spread in epidemics when children are not vaccinated.
convinced that the original results were incorrect. Eventually, investigators determined that the original study was
a fraud. They learned that its author had received a large amount of money to find evidence that the vaccine causes
autism, so he faked his research results. If other scientists had not tried to replicate the research, the truth might
never have come out. You can read more about this case at the URL below.
http://www.usatoday.com/yourlife/health/medical/autism/2011-01-06-autism06_ST_N.htm
Summary
• Getting the same result when an experiment is repeated is called replication. If research results can be
replicated, it means they are more likely to be correct.
• Replication is important in science so scientists can “check their work.” The result of an investigation is
not likely to be well accepted unless the investigation is repeated many times and the same result is always
obtained.
Vocabulary
• replication: Getting the same results when an investigation is repeated.
Practice
Scientists often repeat their own experiments to see if they can replicate the result. These repeated experiments are
called trials. At the following URL, read about the repeated trials in an investigation involving crows. Be sure to
watch the movies showing the crows during different trials. After reading the article and seeing the movies, answer
the questions below.
http://users.ox.ac.uk/ kgroup/tools/tool_manufacture.shtml
1. Why were repeated trials done in this experiment?
2. Why might other researchers in other labs try to replicate the results?
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Concept 1. Replication in Science
Review
1. What is replication?
2. Why is replication important in science?
3. Scientists do not try to replicate every investigation, but some are repeated many times. For example, many
researchers tried to replicate the vaccine-autism study described above. Why do you think so much effort was
made to replicate this particular study? What was the outcome of the additional research?
References
1. Image copyright sergei telegin, 2012. . Used under license from Shutterstock.com
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