Command of evidence: data

Digital SAT · Reading and Writing · Information and Ideas. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

A short text comes with a table. The text ends with a claim or conclusion, and you choose the option that uses the data to support it or to complete it.

Read the claim first and decide what numbers would prove it. Then read the column headings and the units before you read any values.

Each option must pass two tests. Is it accurate: do its numbers match the table exactly? Is it relevant: does it prove this claim and not some other point? Many wrong options quote the table correctly but answer a different question. A claim about a trend or a comparison needs at least two values, not one.

Rules to remember

Read the claim before the table.
For every number in an option, check the row, the column and the unit.
Two tests: accurate (matches the table) and relevant (proves the claim).
A claim with "increases," "decreases," "more than" or "less than" needs two or more values compared.
A claim that a change caused an effect needs a comparison with a group that did not have the change.
A percentage is not a count: 50% of 40 is 20, but 20% of 400 is 80.
A rise from 40% to 46% is a rise of 6 percentage points.

Common mistake

Picking an option whose numbers are correct but which gives only one value when the claim is about a trend or a comparison. One value cannot show a change.

Worked example

A table gives the average height of bean plants after 3 weeks: 2 hours of light a day, 6 cm; 6 hours, 11 cm; 10 hours, 17 cm. A student concludes that plants given more light grew taller. Which statement best supports this: (A) plants given 6 hours of light reached 11 cm, or (B) height rose from 6 cm at 2 hours of light to 17 cm at 10 hours?

The conclusion is about a trend: more light, more height.
(A) is accurate but gives one value only, so it shows no trend.
(B) compares the lowest and highest light levels: 17 − 6 = 11 cm taller with more light.

Answer: (B), because it uses two values that show height rising with light.

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