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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.


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 below). 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.

This child is receiving an MMR vaccine, the childhood vaccine that was linked with autism in a 1998 article. MMR protects children from three different infectious diseases: measles, mumps, and rubella. These diseases spread in epidemics when children are not vaccinated.

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 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.



  • 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.


  • replication: Getting the same results when an investigation is repeated.


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.


  1. Why were repeated trials done in this experiment?
  2. Why might other researchers in other labs try to replicate the results?


  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?

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Date Created:

Oct 31, 2012

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Apr 14, 2014
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