Importance of Controlled Tests in Scientific Research

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  • 0:01 Experiments Are Small Scale
  • 0:59 Controls Limit Other…
  • 3:39 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

One way to ensure that your experimental results are meaningful and relevant is to control for factors that may affect your experiment. In this lesson, we'll talk about how to do this and why it's so important in scientific research.

Experiments Are Small Scale

Scientists are very curious people. We are constantly wondering, questioning, analyzing, and experimenting. We do this because we see processes occurring in the natural world that we want to explain. And one way to try and answer this never ending quest for knowledge is by running experiments.

Experiments allow scientists to recreate conditions on a smaller scale and then apply those answers to the larger-scale world. For example, if you want to know how fertilizer affects plant growth, you don't need to test ALL the plants in the world. Instead, you can test a sample of plants and see how it affects them and then make assumptions on how this would or would not apply to plants you didn't test.

However, there are so many different interactions occurring in the natural world that simply can't be ignored in our experiments. This is why controlled tests are so important in science. These minimize the influence of other variables, helping scientists really hone in on what is going on and why.

Controls Limit Other Influences

Controlled tests are so important because if you don't limit the influences on your experiment, you won't be able to determine why you got the results you did. Take those plants from earlier, for example. If you want to know how fertilizer affects plant growth, you might decide to give half of your plants fertilizer and half of your plants nothing. But other things like sunlight and water influence plant growth as well, so you have to control for these. If the plants get different amounts of sunlight and water, you can't say anything about the influence of fertilizer because you have no idea which of these variables actually influenced your experiment and how!

Instead, you would need to control for both sunlight and water (and anything else that might influence plant growth) by making sure that ALL plants are treated the same in every way but the amount of fertilizer they receive. This way, fertilizer is the only thing that's different in your experiment. And, if you find that your fertilized plants grew more than your non-fertilized plants, you can now say with far more confidence that fertilizer likely had an effect on plant growth because nothing else was different between the two groups.

Let's look at another example, just to make sure you fully understand how important control in your experimental design really is. Let's say that you run a pet store, and you want to know which food your rats prefer so you can recommend that brand to your customers. This sets the stage for a great experiment!

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