Importance of Controls – Biology in the News

Using the article you analyzed for “Biology in the News” summarize the following points:

• What were the results that were obtained (from the experimental system used)?
• What were the controls that were used (which variables were kept constant?)
• What was the purpose for using those specific controls (what does it rule out?)

It’s likely that the controls were not explicitly mentioned in the article, but make an educated guess as to what they would be.  A good hint would also be to look at the journal abstract of the article.

Please be sure your chosen article is an EXPERIMENT. A “study” is often just observational, and no controls are set.

Review BOTH resources below to understand Controls:

Here is a link to information about controlled experiments (Links to an external site.) as presented by the Khan Academy.

Review this power point presentation on The Scientific Method

More helpful information about controls:

How do I determine the controls in the article I chose?  Here is some information to help you:

Let’s suppose you are studying birds and want to learn about their feeding habits. Questions you have may include:

• What time of day do the birds most often come to the feeder?
• What time of the year do birds most often come to the feeder?
• What type of food do the birds prefer (given a finite number of types)?
• Where do birds prefer the feeder to be located?

And there are probably more you can think of. BUT, scientists only set up an experiment to answer ONE question at a time. ALL the other conditions must remain the same. We call those CONTROLS. We can’t accurately come to a conclusion if there is more than one variable at a time.

Take a look at the experimental design chart below. Without any other information, can you tell what variable and controls are set?

The experimenters here must have placed all three feeders in the same place, with the same food, at the same time, in a feeder that has the same construction. The only difference is the color of the feeder. So, the variable they are testing is the color and the controls are the time, shape, food type, and place. When we recorded the results, if there is a significant difference in the amount of food consumed between each of the feeders, we will be able to conclude that COLOR is a significant factor in where birds like to eat.

I found a video showing an experiment that demonstrates all the bulleted points listed above and more. It’s all about testing the “5-second rule”.   DIY Science – The Five-Second Rule.  You can also look up other videos on controls if you have additional questions.

In the above video, pay close attention to

• the controls and reason for them
• the reason for setting up replications of each situation
• how the experiment is set up.