Reading graphs is like reading in a foreign language. It comes easy to some and is very difficult for others. If you struggle to understand graph, tables, and other visuals for ACT Science questions, this article containing tips, strategies, and practice questions is perfect for you.
If you're a “fluent” pro, this article will be a good review to make sure your skills are on point. Even if you are a pro, the ACT Science section often tests the basic skill of reading visuals in new and challenging ways, so this article will make sure you have strategies for both easy and hard questions.
Here is an overview of what we'll cover in this guide:
- Understanding the core elements of a graph
- The importance of labels
- How to use axes
- What to do with units of measure
- Mastering the different types of graphs on the ACT Science section
- Reading bar graphs
- Analyzing scatter plots
- Using line graphs
- Pulling data from tables
- Deciphering tricky graphs
Reading Graphs and Other Visuals Is the Key to Success on the ACT Science Section
Factual Questions Ask You to Evaluate Visuals and Just Relay Information.
These questions simply ask you to relay factual information that is presented in the passage. To answer these questions, you need to read the graphs, tables, and/or scatterplots. For the simplest type of ACT Science practice questions that we'll be covering here, you'll need to pull out specific data points without further calculation/inferences.
These Types of Questions Are Typically Found in Data Representation Passages.
These passages are similar to those found in science journals and text. They present you with a short paragraph or two as well as 1-4 visual representations of data (such as graphs, tables, and/or scatterplots). The passages will mention specific studies and label sections as Study 1/2/3. Each Data Representation Passage has 5 questions, often using the skills we'll be covering here. If you want to learn more about the types of passages and questions on the ACT Science section, check out our article on the 3 Types of ACT Science Passages.
In the PrepScholar ACT Program, we categorize the questions for Data Representation into 3 categories (not everyone categorizes them the same way). Factual questions or “pure data” questions is one of the three types. Here is a sample Data Representation Passage from an ACT practice test:
Here is an example of a factual question from the above passage:
There may be more advanced versions of these questions in which you are asked to look at a weird graph. Such as this one:
Does this graph look crazy to you? Don’t fret! You will master this crazy graph and all others by the end of this article.
Core Elements of a Graph
Let's start off with basic ACT Science tips about the basic components of graphs, and strategies on how to interpret them.
The Importance of Labels
Labels are SUPER IMPORTANT on the ACT Science section. Each visual is labeled with Figure plus a number. So if there are 3 visuals, they will be labeled Figure 1, Figure 2, and Figure 3. See below:
Why are they labeled? So you will refer to the correct one (though many students still don’t look at the right visual). The question will often specifically tell you which figure to look at such as this one:
In Figure 2, what percent of captured finches from Island C had a 10 mm beak depth?
To correctly answer this question, you need to check the labels and make sure you look at Figure 2. Then, identify the graph that shows the finches from Island C. In this case, you need to use the bottom graph. I see the beak depth is along the x-axis. At 10 mm beak depth, I follow the bar up and see it is just short of 35%, so probably about 34%.
The first step in most ACT Science questions is to read the label, and if you get this step wrong, you will get the answer wrong. So make sure you check the label to ensure you are looking at the correct visual for the question.
How to Use Axes
Axes are the lines at the side(s) and bottom of a graph. Axes are useful to figure out the control and the variable(s) in the experiment. I will go into detail on this topic in the examples below.
Graphs by definition have an x-axis and y-axis. The x-axis is the horizontal line (typically at the bottom of the graph). The y-axis is the vertical line (typically on the left side of the graph, though more challenging graphs on the ACT Science will have one on the left and one on the right).
Let’s take a look at this simple graph for practice:
In this graph, the x-axis doesn't measure anything (it only lists animals). In this graph, the y-axis measures the animals’ weights. The animals’ weights would be considered the variable in the research. The researchers did not know what the weights would be exactly until they measured the weights. We can use this graph to compare the 4 elements of only one data set: the weights of animals. If the passage had asked you,
What is the weight of a dog?
First, we need to find dog on the axis that defines the type of animal, which is the x-axis. Next, we look on the y-axis for the value of the dog's weight and see that it reads 10 kg.
Now, for practice, let’s take a look at a slightly more complicated scatterplot with measurements on both axes:
In this graph, the x-axis measures the distance from the center of the plot to the nearest clearing. In this graph, the y-axis measures the average change in AGTB (it is not important to understand what AGTB is).
The average change in AGTB would be considered the "dependent variable" in the research. The researchers did not know what the average change in AGTB would be exactly until they measured it. We can use this graph to compare the distance from the center of the plot to the nearest clearing TO the average change in AGTB. If the passage had asked you,
What is the average change in AGTB at a distance of 50 m from the center of the plot to the nearest clearing?
To do so, we first need to find 50 on the axis that defines the distance from the center of the plot to the nearest clearing, which is the x-axis. Next, we look on the y-axis for the value of the average change in AGTB and see that it reads 5 t/yr.
We will evaluate this graph further in the next portion:
What to Do With Units of Measure
On graphs on the ACT Science section, they will present units of measure for each axis next to the label. Don't try to understand what the units mean. The ACT Science section throws in these crazy, weird units that you won’t have seen unless you studied very high-level Physics or Chemistry. You do not need to know exactly what they refer to in order to answer the questions. Take for example the graph we just discussed:
While you probably know that m is meters, you may be unfamiliar with t/yr, yet you had no problem answering the question above. For the ACT Science section, when the units are listed in the answer choice, they match up to the units shown in one of the visuals or mentioned in the passage (such as in the example above). So, there is no need to dwell on them or stress over them.
In all of the practice sections I’ve ever done or that I’ve ever seen or given to students, I have NEVER seen an ACT Science question ask you to convert the units from one form of measure to another. You most likely were taught this in Math and/or Science classes. Set those skills aside. You do not need them for this test.
Why do the ACT makers include these units if you don’t need them? To make the graph more challenging or to test your ability to sort information that you may not know. Ignore what you don’t need and find the information to answer the question. Focus on what you can identify, which lead us to our next topic:
The Different Types of Graphs
The ACT will show you a variety of graphs. Most of these are predictable. The hardest graphs are graphs that you will never have seen before and have to interpret on the fly. Thankfully, with the clear step by step structure I present below, you'll be able to tackle even the hardest graphs.
Bar graphs tend to be one of the easier visuals used by the ACT Science section. They are easier because there will only be one variable shown. Let’s examine the example practice question below:
In this graph, the x-axis lists the years (in 1-year increments from 1976-1985). The y-axis measures the average beak depth, the variable in this research. We can use this graph to compare the year to average beak depth. If the passage had asked us,
What is the average beak depth in 1983?
First, we need to find 1983 on the x-axis. Next, we look on the y-axis for the value of the average beak depth and see that it reads 9.6 mm. Bar graphs are really easy, so long as you make sure you have identified the correct bar, you will find the data you need.
Scatterplots are graphs of plotted points that show the relationship between two sets of data. We looked at one earlier, but here is another from the same passage:
In this example, each dot represents the measure of the average cumulative percent change in AGTB in a specific year. Let's attempt this practice question:
What was the average cumulative percent change in AGTB during Year 2?
To answer this question, we first need to find Year 2 on the x-axis. Follow that up to the Year 2 point on the scatterplot. Next, we look on the y-axis for the average cumulative percent change in AGTB and see that it reads 6%.
Scatterplots can be slightly more challenging if they ask you a question about a point not marked. Let’s say they had asked you instead:
What was the average cumulative percent change in AGTB during Year 9?
Well, there is no point for Year 9, but you can see the downward trend. In order to answer this question, I recommend drawing on the graph provided. See my example:
Connect the dots you have to create a curve. Sorry for my less than perfect drawing, but you don’t have to be perfect. You can clearly see the curve is much closer to 14% than any of the other options, so the answer is 14%. When answering these trend questions, try whenever possible to draw out the curve on the graph you are given and then use process of elimination.
When in doubt, draw it out. Which our next graphs happen to do for you! Also, check our our articles on calculating questions and interpolations questions!
Line graphs are one of the harder types of visuals used in the ACT Science section. The reason they are more difficult is that they show essentially an infinite number of data points, and you need to be precise about which data point you're looking at. There are so many values since each point on the line is a new value.
Also, the ACT Science section often uses line graphs to show 2 entirely different sets of data, one on the left and one on the right with a key to differentiate between the two lines such as in this example graph:
Let’s break this graph down. 2 lines represent 2 independent groups of information. Each line has its own range of measurements. The x-axis shows time in increments of 5 years. So if you were asked the practice question,
What is the RCRF in January 1990?
You must first notice the correct line. The solid line represents RCRF according to the key. Match it up to the measurement on the right or left. The right side represents RCRF in %. It may help to use the edge of your paper or a pen or pencil to create a straight line to find the point of intersection. See my example:
Then, find the point of intersection between that solid line and the January 1990 mark, which is around 7-7.5% so that is the answer.
So the key ACT Science strategies to remember with line graphs are:
- Identify the correct line
- Match it up to the correct measurement on the left or right
- Draw the point of intersection
Now that we’ve conquered one of the hardest graphs on the ACT Science section, let’s take a break with a simple visual:
Tables are one of the easier types of visuals provided. There are a number of columns, and each entry in a column corresponds to the entry directly to the right or left of that entry in the same row. For example, the below table is typical:
A sample question about a table may look like this:
Based on Table 1, 0.001 ml of titrant added produced a reaction time of?
The answer would be 12 seconds. To find this, you look up 0.001 in the left column representing "Amount of titrant added," and look to the corresponding value on the right, "reaction time."
For tables, the key points are
- Identify the correct column in question
- Find the correct data point in question
- Look to the right or left of it in the same row to find the matching data point
Some tables on the ACT Science section will have many rows and columns of data, but the technique is always the same.
Finally, now that we have grasped most visual concepts, let’s take a whack at:
You should be very close to visual reading “fluency.” Let’s check out a graph that is not what it seems:
A lot of lines with confusing labels. Let’s say we asked a question:
Which of the following absorbed the most light across all wavelengths?
- White S
- Orange S
- Red S
- Brown S
First, let's take a look at the graph. There are 5 lines here, and each one represents a different color of light plus Sulfur Oxide (which we do not need for this question, as it's not one of the answer choices). Each graph represents the reflectance at each wavelength.
The question is asking us for which substance absorbed the most light across all wavelengths. Let's break down this question. First, "absorb the most light" means the opposite of reflectance. Reflectance is what is graphed.
Second, "across all wavelengths" means we're not just looking at one point on the x-axis; we're looking across all points.
The unprepared or rushed student would answer White S because they see it reflects the most light across all wavelengths, of the options in the answer choices.
However, knowing that absorbance is the opposite of reflectance and looking across all wavelengths, I see that Brown S is reflecting the least across all wavelengths. Therefore, it is absorbing the most, so the answer is Brown S.
Rules to remember with graphs: always compare what you are being asked to what the graph actually shows. That way you don’t get tricked!
Let’s check out another tricky graph:
This graph is even more complex. There are intersecting lines of weird shapes, and labels for each of the regions enclosed by lines. But just like every other table, we can attack it one by one.
Let’s say the practice question asked you:
Which of the following would most likely NOT be found at a pressure of 10 kb?
- Facies A
- Facies C
- Facies G
- Facies E
First, let's take a look at the graph. There are 7 Facies identified (facies is a geology term for a body of rock with specified characteristics - this info would be given in the passage). The graph shows the pressure, depth, and temperature at which these 7 Facies appear.
The question is asking us for which of the following is NOT found at a pressure of 10 kb. Let's break down this question. First, pressure means we need to use the left y-axis. Second, we need to find 10 kb. Next, because the question asks what is likely NOT found at a pressure of 10kb, we need to draw a line across it, as in my example:
Now, you can see that Facies C, G, and E all are found out 10kb, but Facies A is not, so A is the correct answer.
The unprepared or rushed student might choose Facies C, G, or E as the answer if they missed the NOT, or that student might accidentally look at a depth of 10 km on the right instead of pressure and get the answer entirely wrong.
What to learn from this,
- Always make sure you have found the correct axis in question
- Be extra careful when you see a NOT or EXCEPT
- This way you avoid getting tricked by referring to the wrong data piece or answering the wrong question!
If you've ever had trouble with interpreting graphs, hopefully, you found this guide useful. Most graphs on the ACT will be of the more simplistic types, but now you should feel confident to tackle even the most complicated graphs the ACT throws at you.
Here's a breakdown of the steps you should take:
- Read labels very carefully. Make sure you're looking at the correct Figure.
- Remember the basics - what the axes represent, how the data points are depicted, how to go step by step to the value you need.
- All of the same rules apply to tables, bar graphs, scatterplots, line graphs, and tricky graphs.
- Don't try to understand the units of measure.
- Practice practice practice to make sure you have these skills down.
I hope you feel like a visual reading pro! As your next steps in studying for the ACT Science section, you should learn the best way to study and practice for ACT Science.
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