As science teachers, we probably  do an awesome job teaching the concept of independent vs. dependent variables to students. But, how many students can actually identify those variables in a lab? Or when given some experimental data? From the results of REAL Science Challenge Volume 2 Contest 3, approximately 50% of participants struggle to identify independent and dependent variables from experimental data. So, how can we help students apply what they know with regards to independent and dependent variables? How can students identify independent and dependent variables in situations other than those we give them?

In this resource, we discuss the language and conventions we use in presenting science experiments and results. As science teachers, we don’t notice these conventions because we’re so used to them. They’re like little tips science teachers have grown accustomed to. But, these conventions help us to decipher important information like independent and dependent variables. And, by teaching students these same conventions, they’ll be being able to extract the same information regardless of what data is given. We have a cheat sheet available for download at the end of this post.

What are Independent and Dependent variables?

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.

Thus, one way to identify independent and dependent variables is to refer to the experimental procedure. Ask, what is the researcher changing between trials or is planning to alter during their research? This is the independent variable. Also, ask, what change is the researcher trying to measure to determine the effectiveness of their experiment? This is the dependent variable.

How else to identify independent and dependent variables

In the title

A common structure to the title of a science experiment goes like this: “The effect of x on y”.

For example, “The effect of climate change on the migratory patterns of ducks”.

More specifically, the common structure of the title is one that goes like this: “The effect of <independent variable> on <dependent variable>.”

Therefore, in our title example above, the independent variable in the experiment is climate change (and likely aspects of climate change like temperature). And, the dependent variable for the same experiment is migratory patterns of ducks.

In the graph

The structure of a graph – be it a bar graph or linear graph – will have one variable plot along the x-axis and another on the y-axis.

For example, the following graph is a climatograph for a specific biome.

The value plot along the x-axis – months of the year – is the independent variable. The value – or, in this case, values – plot on the y-axis are the dependent variables. There are 2 for this graph: temperature and precipitation.

In the hypothesis

The structure of the typical testable, predictive hypothesis is an “If…then…” statement.

For example, “If the temperature of the liquid increases, then the time it takes salt to dissolve decreases.”

More specifically, the structure of the typical, testable hypothesis is a statement that goes like this: “If <independent variable> increases/decreases, then <dependent variable> increases/decreases.”

Therefore, in our hypothesis example above, the independent variable for the experiment is temperature of the liquid and the dependent variable is the time it takes salt to dissolve.

Wrap Up

Our job as science teachers is to teach science literacy. We teach not just the content but the language of how that content is presented. By teaching the structure of that language, the conventions that scientists use, we make science easier (and, hopefully, quicker) for students to grasp. The conventions we wrote about in this resource represent just a few. There are many more we can present to our students. Click on the link below to download our handouts to this post.

Until next time, keep it REAL.

Resources

Handout(s): 34 – 3 Tips to Identify IV and DV

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