How to read charts and graphs on the GED

Start with the title, axes, units, and legend

Most mistakes on graph questions happen before any math is done. A test taker glances at the bars, picks the tallest one, and misses that the graph measures something different from what they assumed. Spend ten seconds on the frame of the graphic first.

The title tells you what is being measured and often the place and time period. The horizontal axis usually shows categories or time. The vertical axis shows the amount. Check the units on each axis: dollars or thousands of dollars, people or percent of people, miles or kilometers. A label such as “Population (thousands)” means a reading of 40 is really 40,000. The legend, or key, tells you what each color or line pattern stands for when more than one data set is shown.

• Title: what, where, and when.
• Axes: what each direction measures.
• Units and scale: what one grid line is worth.
• Legend: which color or symbol belongs to which group.

Bar, line, and circle graphs, and tables

Bar graphs compare amounts across categories, such as sales by store or rainfall by month. Read the top of each bar against the vertical axis. If a bar falls between grid lines, estimate, and expect the answer choices to be far enough apart that a careful estimate works.

Line graphs show change over time. A rising line means the amount is increasing; a steeper line means it is changing faster. Questions often ask when the change was greatest, which means finding the steepest section, not the highest point.

Circle graphs, or pie charts, show parts of a whole. The slices add up to 100 percent. To find an actual amount, multiply the slice’s percent by the total, which is usually given in the title or the question.

Tables give exact numbers in rows and columns. Read the row and column headings before you look at any numbers, and use your finger or the cursor to stay in the right row. Tables are often where the GED asks for a mean, a median, or a rate of change.

Scatter plots, correlation, and causation

A scatter plot shows pairs of values as dots, such as hours studied and test score for each student. If the dots trend upward from left to right, the relationship is positive: as one value goes up, the other tends to go up. A downward trend is negative. Dots with no clear pattern show little or no relationship.

A relationship between two variables is a correlation. It does not prove that one causes the other. Ice cream sales and drowning rates both rise in summer, but ice cream does not cause drowning; hot weather affects both. GED Science and Social Studies questions often include an answer choice that turns a correlation into a cause. Unless the data comes from a controlled experiment, be cautious about any choice that says one thing caused another.

How graphics appear in each subject

In Math, graphics are mostly a source of numbers. You might read two values from a line graph and find the rate of change, find the mean from a table, or figure out the amount a slice of a circle graph represents.

In Science, graphics usually come from an experiment or a study. You may need to identify the independent variable on the horizontal axis and the dependent variable on the vertical axis, describe a trend, or choose the conclusion the data supports.

In Social Studies, graphics describe people, places, and economies: population changes, election results, budgets, or unemployment rates. The correct answer is the one the graphic supports, not a statement that is true in general but not shown in the data.