Visual sources invite overstatement because the display can look more decisive than the data are. Read the labels and units before writing a claim, then check which population and time period the figure actually covers. Use only the conclusion the display supports.
Read the variable before reading the trend
Before interpreting what a chart shows changing, identify exactly what is being measured. A chart's trend line means nothing until you know precisely what variable that line represents, and confusing a related variable for the one actually shown produces a claim the chart does not support.
Check the units before comparing values
Two numbers cannot be meaningfully compared unless they share the same units. A count of patrons is not the same kind of value as a percentage of patrons, and treating them as interchangeable produces a comparison the data does not actually make.
Find the population the data actually represent
A chart's population, who or what was actually measured, limits how broadly its findings can be applied. Data drawn from one county cannot be presented as describing an entire state or country without additional support.
Keep the time window inside the claim
A chart's data was collected during a specific time window, and any claim built from it should stay inside that window unless another source establishes that the pattern continued. A single year's data does not, by itself, establish a long-term trend.
Separate count from rate
A raw count, how many, and a rate, what proportion, answer different questions and can even point in different directions. A group can have a high count of late returns simply because it is a large group, while having a low rate of late returns relative to its size. Confusing the two produces a misleading claim.
Refuse to turn correlation into cause
A chart showing that two variables move together, income bracket and late-return rates, for instance, does not by itself establish that one causes the other. Other explanations, access to transportation, work schedules, or distance from a branch, could also explain a correlation the chart shows without confirming a causal claim the chart itself never makes.
Read the display type before interpreting it
For a graph, read the axis labels and scale. For a table, identify the row and column units and the denominator behind any rate. For a map, read the legend and geographic unit. Then state only the relationship the display actually shows.
Connect the visual to another source only when the evidence permits it
Combining a visual source's finding with a claim from a different source can strengthen an essay, but only when the two sources actually address the same specific population, variable, and time period closely enough to be connected without overstating either one.
Exam Diamond
State the smallest accurate claim a visual source supports: the exact variable, in its actual units, for its specific population and time window. A dramatic overstatement is weaker than a precise limitation.