Reading & Writing · Information and Ideas

Command of Evidence

Identify the claim before selecting evidence. The best evidence must support or weaken that exact claim, with the right comparison and direction; a fact about the same topic is not enough.

Written by Luke Finigan
2 min readUpdated

State the claim in testable terms

Suppose a researcher claims a coating reduces metal corrosion. Evidence comparing coated and uncoated metal under the same conditions directly tests that claim. Evidence that the coating is inexpensive may matter commercially, but does not support reduced corrosion.

Write the predicted difference: coated samples should corrode less. For a weakening question, look for evidence that undermines that difference or reveals a competing explanation.

Match evidence to the comparison

Imagine coated samples lose 2 grams and uncoated samples lose 7 grams during the same exposure. That difference supports the coating claim. If coated samples lose 2 grams in dry air and uncoated samples lose 7 grams in salt water, the environments differ as well as the treatment.

The second comparison leaves an alternative explanation. Read conditions, groups, and timing rather than selecting the most dramatic numerical contrast.

Read graph labels before evaluating a statement

A chart might report percentages rather than counts, or changes rather than final values. If Group A rises from 10 to 20 while Group B rises from 30 to 35, A has the larger increase but B still has the larger final value.

Compare the exact quantities named in the choice. Check units, legend, and relevant points before interpreting a pattern. Evidence about one subgroup cannot automatically support a claim about all groups.

Use textual evidence for the specified trait or claim

If a character is described as cautious, a quotation showing that the character checks a bridge before crossing supports that trait. A quotation showing that the character owns a map may be consistent with caution but is less direct.

After a miss, write a "because" sentence joining the evidence to the claim. If that link requires adding an unstated assumption, the evidence may not do the job the stem requests.

Check your understanding

Try it yourself

A claim says a fertilizer increases plant height. Which comparison most directly supports it?

Sample command of evidence questions

Command of Evidence · Easy

A conservation report gives the number of nesting pairs recorded in four wetlands: Wetland A, 18; Wetland B, 31; Wetland C, 27; Wetland D, 22. Which statement is supported by the data?

Command of Evidence · Easy

Which quotation from The Wonderful Wizard of Oz most effectively illustrates the claim?
The Wonderful Wizard of Oz is a 1900 novel by L. Frank Baum. In the novel, the narrator describes a character's house as having become very faded in appearance over time: ______

Command of Evidence · Easy

While studying water use in greenhouse farming, a student compares two irrigation schedules applied to identical tomato beds. The student concludes that the North schedule conserved water without substantially reducing the crop yield. Which finding best supports this conclusion?

Practice this skill

  1. Translate the claim into a predicted observation.
  2. Check group, condition, direction, and units in each evidence choice.
  3. Explain why the selected evidence bears directly on the claim.
Practice command of evidence

Print the command of evidence worksheet and worked answers.

Then use a mixed practice module to check whether you can choose this method among other question types.

Source and question labels

The bank label for this guide is "Command of Evidence" in Information and Ideas. The worked examples above are written for this guide.

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