How to Avoid Bias in Scientific Investigations

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  • 0:01 A Scientific Invesigation
  • 1:02 Is Your Investigation Biased?
  • 2:25 Avoiding Bias
  • 3:25 A Proper Investigation
  • 4:05 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this lesson, you will learn what it takes to conduct a proper scientific investigation while doing your best to avoid any possibility of bias. Learn where possible sources of bias can come from and what you can do about it.

A Scientific Investigation

In this lesson, we will talk about what it takes to conduct a scientific investigation that is as free from bias as possible. A scientific investigation is a study conducted to answer questions. Bias is a prejudice in favor towards people or things.

Now, imagine that you are a scientific researcher. You've been given the task of performing a survey to find out whether people in a certain geographic area experience more or less headaches when compared to people from other areas.

See, the people in this particular area happen to be the only people group that eats a certain native plant.


People who live in other areas won't touch this native plant because it looks scary with its bright red leaves and spikes. They also say this plant causes major headaches. However, when you went to visit this particular area, nobody seemed to be suffering at all. Everybody looked calm and happy. Nobody was grabbing his or her head in pain. It's now your job to conduct a scientific investigation to find out whether the claim that this plant causes headaches is valid or not.

Is your Investigation Biased?

To conduct a proper scientific investigation, you need to make sure that your investigation is free from bias. You begin to think about the investigation you are about to conduct and ask yourself if your investigation is biased.

Right now, you are planning to conduct the survey by asking all the people you know that live in that particular area whether they eat the plant and whether they suffer from headaches. You have a rather large number of family members living there, as well as a few friends, which is how you found out about this plant in the first place. So right now, your survey consists of your family and friends. The questions you are asking are neutral; you are not assuming any particular lifestyle, and your surveys will not have names attached to them.

Now that you have set up some preliminary guidelines for your study, it is time to ask yourself whether your investigation is biased or not. You start thinking perhaps it might be biased. After all, the only people being surveyed are your family and friends. This could be considered biased because you are not including a random sample of people from that particular area. If you include only your family and friends, your results may not fully represent the true picture because there could be other commonalities having to do with lifestyle. Your family and friends may do some things that other people don't or abstain from behaviors other people engage in, both of which could impact the number of headaches they experience.

Avoiding Bias

You remember that in order to avoid bias, you need to get the full picture by including people from all lifestyles that live in that area because you know that your choice of participants is one possible source of bias. You also realize that you need to include people from outside the area so that you have something to compare your answers to.

You now look over the questions that you are planning to ask to look for additional sources of bias. These look okay because the questions don't assume a particular lifestyle, etc. They are straightforward questions. None of the surveys will have names attached to them, so the only information the survey will be connected to is whether the person is from the particular area or not.

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