Understanding the ways data can be represented in graphs and charts is a key part of comprehending math and science. It is also an essential skill on the ACT math and science sections.
The visuals by themselves are not especially complicated; rather, the challenge lies in the immense time-related pressure of the ACT format. You will have a minute or less per question. This includes reading any background material for sets of questions, as well as arriving at individual answers.
How can you maximize this time per question? By familiarizing yourself with the visuals you will encounter and the concepts that apply to them and then practicing your interpretation.
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1. Learn the most common types of visuals: In the worlds of math and science, there are four basic types of visuals: pie charts, bar graphs, line graphs and scatter plots. Each graph is used to display a specific type of data.
A pie chart, for example, represents proportions. Pie charts typically do not display counts or numbers of items, although the total number of objects is generally noted on the side of the visual. Thus, a wedge that represents 20 percent of a group of 300 students would be equivalent to 60 students.
The other three categories of visuals rely on rectangular plots with x and y axes. It is important to note, however, that the axes will vary in what they represent.
Bar graphs, for instance, display actual counts of different categories of items. Consider a group of 300 students, each wearing a sweatshirt in one primary color. The x, or horizontal, axis would list blue sweatshirts, green sweatshirts, red sweatshirts, etc. The vertical, or y, axis would have the corresponding counts of students wearing each color, and the bar height would be equal to the count.
Line graphs are used to show the relationship between two variables, where one variable is presumed to cause a change in the other. For example, a line graph might display the number of days after the start of the fall semester — along the x-axis — and how many total students are wearing sweatshirts, on the y-axis. The implication is that more students will wear sweatshirts as the year progresses and as the weather grows colder.
A scatter plot is used to find or display a relationship between two variables where one does not necessarily influence the other. You might use a scatter plot to graph the number of students wearing sweatshirts on one axis and the number wearing hats on the other.
If both increase, you might hypothesize that colder weather causes people to wear hats and sweatshirts. In other words, the increase in sweatshirts is not causing the increase in hats. Rather, both are caused by the same factor — colder temperatures.
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2. Learn which concepts apply to which visuals: Understanding the uses of each visual is vital for gaining an edge on the ACT math and science portions. For instance, pie charts generally involve questions that are focused on percents and ratios.
Be very aware of not just the pie wedges but also the total number of items represented by the pie. Twenty percent of 600 is a much smaller number than 20 percent of 10,000.
Bar charts are used for questions that are focused on numbers. Interpreting a bar chart is usually a simple numbers game. Find the category names on the x-axis and then the corresponding values on the y-axis.
Line graphs and scatter plots generally call for the most sophisticated interpretation. The simplest use is to pull values out: Given a certain x- or y-axis value, can you find the corresponding value on the opposite axis? More complicated uses include forecasting based on past trends in data — or extrapolation — and estimating values that fall between data points, or interpolation.
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3. Practice interpreting visuals: As you practice for the ACT, try to classify each visual that you encounter — whether on a sample test, in your classes or in the everyday life. Ask yourself why that type of visual was used for that particular data set.
If you aren’t completing a timed run-through of the ACT, try sketching the visual in alternate formats. Converting a bar graph to a pie chart and vice versa is relatively simple and can further suggest the merits of each visual.
As you become more familiar with reading charts and graphs, you should be able to answer many questions by simply looking at the accompanying visual. You may even find that you need less time to find the correct answers to a group of questions — the point of a visual, after all, is to summarize a lengthy passage into one coherent picture.
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Improve Interpretation of Visuals for ACT Math, Science Success originally appeared on usnews.com
