3.3 Command of Evidence: Quantitative

The Command of Evidence: Quantitative sub-point puts an informational graphic in front of you and asks you to use the data to support, undermine, or complete a claim. College Board restricts R&W graphics to exactly three forms — tables, bar graphs, and line graphs — so you will never face a pie chart, a scatterplot, or an infographic here. College Board also states that these questions require no prior subject knowledge and no advanced computation: they reward careful reading of labels and units far more than they reward math.

Two Question Flavors

1. Support/undermine a claim using the data. The passage states a claim; you must choose the choice that the data most strongly supports or that most weakens it.
2. Complete a sentence using the data. A sentence is written with a blank (often expressed as "the data in the graph support the claim that ____"), and you choose the option that the graphic actually shows.

Strategy: Claim → Data → Compare

1. Read the claim first. Identify the specific trend, comparison, or value the claim asserts. Note the variables and the direction.
2. Read the graphic's labels, units, and legend before the data. What is on each axis? Is the y-axis in thousands, millions, percent, or index points? Does the legend show multiple series?
3. Find the relevant data points. Match the variables in the claim to the variables in the graphic.
4. Compare. Does the data show what the claim says? For a support question, the choice that restates the graphic accurately is correct. For a weaken question, the choice that the graphic contradicts is correct.

The Four Common Traps

Reading Labels: A Habit

Before you read a single data point, answer three questions in order:

1. What variable is on the x-axis, and what are its units?
2. What variable is on the y-axis, and what are its units?
3. What does each series or bar group represent?

If you skip this step, you are guessing. The test writers deliberately design traps around misread axes and units because they know most errors come from there, not from arithmetic.

Worked Example

The claim: "Between 2015 and 2020, U.S. electricity generation from wind power rose, while generation from coal fell but still exceeded wind in absolute terms."

Data (U.S. net generation, all sectors, in billions of kilowatt-hours; U.S. Energy Information Administration, Electric Power Annual):

Question: Which choice is best supported by the data in the table?

• A. Wind generation surpassed coal generation by 2020. (false — coal, at 773, is still more than twice wind's 338)
• B. Wind generation rose between 2015 and 2020, but coal generation remained higher in absolute terms. (correct — matches both parts of the claim)
• C. Coal generation rose between 2015 and 2020. (false — coal fell from 1,352 to 773)
• D. Wind generation grew by more than 200 billion kWh between 2015 and 2020. (false — the increase is 338 − 191 = 147 billion kWh, less than 200)

B is correct because both pieces — the rise in wind, and the fact that coal still exceeds wind in absolute terms in 2020 — are directly visible in the table. The wrong choices each misread either direction (A, C) or magnitude (D).

A Note on Units

SAT graphics frequently mix units across series or use scaled axes (for example, a line graph whose y-axis starts at a non-zero value). A bar that looks twice as tall may represent only a 20% increase if the axis starts at 80 rather than 0. Always check the baseline of any chart before comparing bar heights visually.

Key Takeaways

• Read labels, units, and the legend before reading any data point.
• Match the variables in the claim to the variables in the graphic.
• For weaken items, find the choice the graphic contradicts, not the one that feels wrong.
• Compare whole trends, not single convenient points.