What’s one thing science students should be able to do in grade 8 and 9? I think they should be able to identify and differentiate between independent and dependent variables. However, many gr 8 and 9 science students struggle with this skill. Results from REAL Science Challenge contests show that over 40% of contest writers are unable to identify independent and dependent variables in an experiment. That’s 2 in 5 students who struggle with this skill (or 12 students in a class of 30).

Without being able to Identify and/or distinguish variables, how can students have a proper discussion of experimental design or error when it comes to lab results? How can we expect students to design their own labs without first knowing what variables in an experiment to measure or to manipulate?

In this resource, we give a quick crash course on independent and dependent variables through the fun analogy of making a great movie. Our cheat sheet will be available for download at the end.

What is an Independent & Dependent variable?

An independent variable is the condition or factor a scientist changes during the experiment.

A dependent variable is the condition or factor a scientist measures in order to study the effects of the changes made to the independent variable.

Both independent and dependent variables are conditions the scientist measures and conditions in an experiment that change. But, independent variables are usually set or altered by the researcher to test an idea while dependent variables are measured during or after the experiment. In other words, a researcher can control or preset independent variables, while a researcher cannot preset a dependent variable.

Variables and How to Make a Great Movie

Imagine you’re a movie producer looking to make the next hugely successful movie. There are two questions you want to consider. First, what conditions help make movies become successful? And, secondly, how can we tell if a movie is successful or not?

Let’s consider the first question: What conditions help make a movie be successful? There are many potential answers for this. Perhaps, spending more money on producing the movie will help make the movie successful. Or, maybe hiring a lot of Oscar winning actors will make a movie successful. Maybe, having more visual effects will make a movie successful. There are many answers to the question, and many conditions we can test to get an answer. These conditions, which we can alter and test – conditions like money spent or actors hired – are examples of independent variables. Note that all the examples above are conditions that a movie producer can preset or control in the making of their movie.

Now, let’s consider the second question: How can we tell if a movie is great or not? Again, there are many things we can measure to find the answer.Perhaps, we can measure the amount of tickets sold to determine the success of a movie. Or, maybe, we can measure how many awards a movie wins to rate a movies success. Or, we can also use audience and critics’ reviews on RottenTomatoes.com for our measure. Again, there are many things we can measure, and many ways to answer the question. The takeaway is that the dependent variable in an experiment is what we measure (whether it be awards won or tickets sold) to determine the effectiveness of the changes done to the experiment (whether it be spending more money or using more visual effects). Also, take note that all the examples in this paragraph are conditions that a movie producer cannot preset or control. Movie producers cannot predetermine how much money they will make or how many awards they will win for a movie.

Wrap Up

The concept of the independent and the dependent variable is central to experimental design. Therefore, it’s important to have students understand the concept early in their science career. Also, it helps to have fun, relevant examples to learn from (like making movies) and practice with too. The latter is something we’ll be providing in the next post. Click the link below to download a copy of our cheat sheet for this crash course on independent and dependent variables.

Until next time, keep it REAL.

Resources

Handout(s): 25 – Variables Cheat Sheet

Our resources are free. We aren’t collecting emails for our resources. However, it would help us out if you liked us on our Facebook page and subscribed to our Youtube Channel. Thanks!