Command of Evidence — Textual and Quantitative

Command of Evidence — Textual and Quantitative

SAT Reading and Writing — Information and Ideas

Learning Objectives

By the end of this lesson, you should be able to:

• Identify claims, arguments, and conclusions in passages.

• Recognize evidence that directly supports a claim.

• Select the strongest textual evidence.

• Distinguish relevant evidence from unrelated information.

• Identify evidence that weakens or challenges a hypothesis.

• Interpret data in tables and graphs.

• Compare numerical values, percentages, and changes.

• Select quantitative evidence that supports a stated conclusion.

• Recognize when evidence is insufficient.

• Eliminate misleading SAT answer choices.

1. What Is Command of Evidence?

Command of Evidence measures your ability to understand how information supports a claim or conclusion.

A claim is a statement that an author or researcher argues is true.

Evidence consists of facts, observations, examples, measurements, quotations, or research findings used to support or challenge that claim.

In SAT Reading and Writing, you may be asked to determine which information best:

• Supports a claim

• Illustrates an argument

• Strengthens a hypothesis

• Challenges an explanation

• Demonstrates a research finding

• Completes a passage using evidence from a table or graph

Example

Claim: Regular access to green spaces may improve people's well-being.

Evidence: In a survey, residents who visited local parks several times each week reported higher levels of satisfaction with their neighborhoods than residents who rarely visited parks.

This evidence supports an association between park use and reported well-being.

However, it does not by itself prove that park visits caused the differences.

Important: Evidence must support the specific claim being made, not merely discuss the same subject.

2. Two Types of Command of Evidence Questions

A. Textual Evidence

These questions provide a passage and ask which information best supports, illustrates, or challenges a claim.

You may need to choose a quotation, finding, or hypothetical observation.

Example

A researcher argues that certain birds can adjust their nesting behavior in response to changing temperatures.

Which finding would best support this claim?

A. The birds have colorful feathers.

B. The birds build nests at different heights during warmer and cooler seasons.

C. The birds eat several types of insects.

D. The birds live in multiple geographic regions.

Correct Answer: B

The evidence directly connects nesting behavior to changes in temperature.

The other choices describe the birds but do not establish the relationship in the claim.

B. Quantitative Evidence

These questions require you to interpret numerical data, often presented in a table or graph.

Example

A scientist compares plant growth under different light conditions.

Claim: Increasing light exposure from 4 to 8 hours per day was associated with greater plant growth.

Supporting Evidence: Average height increased from 12 cm to 23 cm.

This directly supports the stated comparison.

SAT Tip: Identify exactly which measurements the claim compares before examining the choices.

3. Identifying the Claim

Before selecting evidence, determine what the claim actually says.

Claims often contain several important components:

1. The subject being studied

2. The relationship or effect being proposed

3. The conditions under which it occurs

4. The scope or strength of the conclusion

Example

Claim: Certain aquatic plants grow faster in moderately warm water than in cold water.

Key components:

• Subject: Certain aquatic plants

• Comparison: Moderately warm versus cold water

• Outcome: Growth rate

• Direction: Faster in moderately warm water

Strong supporting evidence must address these specific components.

Evidence that the plants survive in warm water is related but does not necessarily demonstrate that they grow faster.

4. Choosing the Strongest Textual Evidence

A strong piece of evidence directly establishes an important part of the claim.

Example

Claim: A novelist's later works placed greater emphasis on ordinary people's experiences than the novelist's earlier works.

Which finding best supports the claim?

A. The novelist published books in several cities.

B. The novelist frequently attended literary meetings.

C. The later novels feature working-class characters more prominently than the earlier novels.

D. The novelist used descriptive language throughout the career.

Correct Answer: C

Choice C directly compares the earlier and later works in terms of the subjects emphasized.

The other choices provide biographical or stylistic information but do not support the central comparison.

Key Principle

The strongest evidence usually addresses the relationship or distinction in the claim, not just its general topic.

5. Relevant Evidence vs. Irrelevant Evidence

Evidence may be factually correct but irrelevant to the claim.

Example

Claim: A new coating makes metal surfaces more resistant to corrosion.

Possible findings:

1. The coating is transparent.

2. Coated metal samples showed less rust after repeated moisture exposure than uncoated samples.

3. The coating can be applied using a spray.

4. The researchers worked at a university.

Finding 2 is the strongest evidence.

The other findings may be true, but they do not directly establish corrosion resistance.

SAT Tip: Ask, "If this evidence were true, would it actually make the claim more convincing?"

6. Supporting vs. Weakening Evidence

Not every Command of Evidence question asks you to support a claim.

Some questions ask for evidence that would weaken, challenge, or undermine an explanation.

Example

Hypothesis: A species of butterfly selects flowers mainly according to their color.

Supporting Finding: Butterflies consistently visit blue flowers more often than otherwise similar flowers of other colors.

Challenging Finding: Butterflies visit flowers of different colors at similar rates when those flowers produce the same scent, but their choices change substantially when scent varies.

The challenging finding suggests that scent may be more important than color.

Strategy

Check the direction of the question.

• Support: Look for confirming evidence.

• Weaken: Look for contradictory or alternative evidence.

• Illustrate: Look for an example of the stated claim.

• Demonstrate: Look for a result that directly establishes the described pattern.

7. Evidence and Scientific Hypotheses

Science passages frequently present a hypothesis and then ask which result would support it.

A hypothesis is a proposed explanation that can be investigated.

Example

Researchers hypothesize that a certain desert insect avoids midday activity to reduce exposure to high temperatures.

Strong supporting evidence would show that the insect's activity is lower during hotter conditions, ideally while alternative factors are controlled or considered.

A finding about the insect's body color would not directly support this temperature-related explanation.

Important Distinction

Evidence can support a hypothesis without proving it beyond all doubt.

In your answer, preserve words such as:

• May

• Suggests

• Is associated with

• Is consistent with

• Provides evidence for

Avoid interpreting a limited observation as universal proof.

8. Comparative Claims

Many SAT questions require evidence comparing two groups, time periods, or conditions.

Example

Claim: A redesigned solar panel produces more electricity under low-light conditions than an older model.

The strongest evidence for the stated claim is:

Under low-light conditions, the redesigned panel produced 62 W compared with 45 W for the older panel.

Although the redesigned panel also performs better under the other conditions, the claim specifically concerns low light.

SAT Tip: Match the comparison in the evidence to the comparison in the claim.

9. Quantitative Evidence From Tables

A table organizes data into rows and columns.

Before analyzing the data:

1. Read the table title.

2. Identify the row categories.

3. Read the column headings.

4. Check the units.

5. Identify the values relevant to the claim.

6. Compare the appropriate quantities.

Example

A study examines average daily water consumption.

Claim: All three buildings used less water after the improvements.

Check:

Building A: 390 < 480

Building B: 430 < 520

Building C: 360 < 450

The table supports the claim because consumption decreased in every building.

Common Trap

Do not compare values from different rows or categories unless the claim requires that comparison.

10. Quantitative Evidence From Graphs

SAT questions may include bar graphs, line graphs, or scatterplots.

Bar Graphs

Bar graphs usually compare categories.

Look for:

• Highest and lowest values

• Differences between groups

• Categories increasing or decreasing

• Comparisons across periods

Line Graphs

Line graphs often show changes over time.

Look for:

• Overall trends

• Increases and decreases

• Peak values

• Changes in rates

• Differences between series

Scatterplots

Scatterplots show paired numerical observations.

Look for:

• Positive or negative associations

• Strong or weak trends

• Outliers

• Relationships between two variables

SAT Tip: A graph may contain more information than you need. Focus only on the data required by the question.

11. Understanding Percentages

Quantitative evidence questions sometimes require comparisons involving percentages.

Example

A school's recycling participation increased from 40% to 55%.

The increase is:

55% − 40% = 15 percentage points

The relative percentage increase is:

(55 − 40) / 40 × 100 = 37.5%

These quantities are not interchangeable.

Important Rule

A change from 40% to 55% is:

• An increase of 15 percentage points

• A relative increase of 37.5%

Always check which type of change the question describes.

12. Comparing Absolute and Relative Changes

A difference in actual values is called an absolute change.

Absolute change = New value − Original value

A percentage change compares the difference with the original value.

Percentage change = (New − Original) / Original × 100%

Example

A program's enrollment increases from 200 students to 250 students.

Absolute increase:

250 − 200 = 50 students

Percentage increase:

50/200 × 100 = 25%

SAT Tip: Larger absolute increases do not always correspond to larger percentage increases.

13. Claims Involving Maximums and Minimums

When a claim says a category has the greatest or smallest value, compare all relevant categories.

Example

Claim: Method B had the shortest average completion time.

The table supports the claim because 12 minutes is the smallest value.

A common mistake is confusing shortest time with lowest performance. Always interpret the meaning of the measurement.

14. Claims Involving Trends

Trend claims often use phrases such as:

• Generally increased

• Consistently decreased

• Remained approximately stable

• Increased more rapidly

• Declined after reaching a peak

Example

The number of visitors increased overall from 2021 to 2024.

However, it did not increase every year because there was a decrease between 2022 and 2023.

Important: "Increased overall" and "increased every year" are different claims.

15. Correlation Does Not Establish Causation

Quantitative evidence may demonstrate an association without establishing a cause-and-effect relationship.

Example

Researchers observe that neighborhoods with more parks tend to report higher physical activity rates.

This supports an association between park access and physical activity.

It does not automatically prove that adding a park would cause every resident to exercise more.

Other factors may influence both variables.

When selecting evidence, do not strengthen a claim beyond what the data support.

16. Insufficient Evidence

Sometimes evidence provides useful information but does not establish the complete claim.

Example

Claim: A new educational program improves mathematics and reading performance.

A study reports improvement in mathematics scores but provides no reading results.

The evidence supports only part of the claim.

It does not establish an improvement in reading.

Key Principle

Evidence must address all essential components of the claim.

A result supporting one part of a two-part claim may be insufficient.

17. Common Incorrect Answer Types

A. True but Irrelevant

The statement is true according to the passage but does not support the claim.

B. Reversed Relationship

The answer describes the opposite of what the evidence indicates.

C. Unsupported Generalization

The answer extends findings beyond the population or conditions studied.

D. Incorrect Comparison

The answer compares the wrong categories, years, or measurements.

E. Misread Numerical Data

The answer uses a value incorrectly or confuses percentages, units, or changes.

F. Insufficient Evidence

The answer supports only part of the claim or does not establish the stated relationship.

18. Worked SAT-Style Examples

Example 1 — Textual Evidence

Passage

Environmental researcher Maya Chen argues that some urban birds have adapted their feeding schedules to human activity. Chen suggests that birds may avoid heavily used public areas during the busiest hours.

Question

Which finding would most directly support Chen's claim?

A. The birds have brightly colored feathers.

B. The birds feed in public squares more frequently before sunrise than during peak pedestrian hours.

C. The birds are found in several countries.

D. Public squares contain a variety of trees.

Correct Answer: B

Explanation

Step 1: Identify the claim: feeding schedules change in response to human activity.

Step 2: Look for evidence comparing feeding behavior at different activity levels.

Step 3: Choice B directly links feeding times with pedestrian activity.

Example 2 — Weakening a Hypothesis

Passage

A researcher hypothesizes that a certain plant grows more rapidly in shaded areas because shade reduces water loss.

Question

Which result would most directly weaken this hypothesis?

A. Plants in shaded areas receive less direct sunlight.

B. The studied plant grows equally well in shade and sunlight when soil moisture is controlled.

C. Some plants have deep root systems.

D. Shaded areas may have different soil temperatures.

Correct Answer: B

Explanation

Step 1: The hypothesis links shade to faster growth through reduced water loss.

Step 2: Choice B shows that when moisture is controlled, shade does not improve growth.

Step 3: This challenges the proposed explanation.

Example 3 — Quantitative Evidence

Table: Average Plant Height After Four Weeks

Claim: Fertilizer B produced the greatest average plant height.

Correct supporting evidence: Plants treated with Fertilizer B had an average height of 21 cm, higher than every other group.

Example 4 — Percentage Comparison

Table: Library Membership

Question: What was the percentage increase?

Solution

Increase = 1,000 − 800 = 200

Percentage increase = 200/800 × 100

Answer: 25%

Example 5 — Overall Trend

Table: Museum Visitors

Claim: Museum attendance increased overall between 2021 and 2024, despite a temporary decline.

Supporting evidence: Attendance rose from 4,200 to 5,500, although it decreased between 2022 and 2023.

This is stronger evidence than saying attendance increased every year, which the table contradicts.

19. SAT Strategy for Command of Evidence

Use this five-step method:

Step 1: Read the claim carefully.

Identify the subject, comparison, and proposed relationship.

Step 2: Determine what type of evidence is needed.

Is the question asking for textual support, a challenge to a hypothesis, or numerical evidence?

Step 3: Predict what supporting evidence would look like.

Before reading the answer choices, identify the type of finding that would directly address the claim.

Step 4: Evaluate the answer choices.

Eliminate choices that are irrelevant, contradictory, too broad, or numerically incorrect.

Step 5: Verify the relationship.

Ask whether the evidence genuinely supports the precise claim without introducing extra assumptions.

20. Common SAT Mistakes

• Selecting evidence that discusses the topic but does not support the claim.

• Choosing a true statement that is irrelevant.

• Confusing evidence that supports a claim with evidence that challenges it.

• Ignoring important qualifications in a hypothesis.

• Comparing the wrong rows or columns in a table.

• Confusing an overall increase with an increase in every period.

• Misreading the units on a graph.

• Confusing percentage points with percentage change.

• Assuming correlation proves causation.

• Choosing the largest numerical value without checking the question.

• Ignoring evidence that contradicts a proposed explanation.

• Accepting a conclusion broader than the data support.

• Selecting an answer that supports only part of a claim.

• Rushing through numerical comparisons without verifying the values.

21. Final Revision Checklist

Before attempting practice questions, make sure you can:

• Identify claims and hypotheses.

• Recognize directly relevant textual evidence.

• Select evidence that supports or weakens a claim.

• Read tables and graphs accurately.

• Compare categories and numerical values.

• Interpret percentages and changes.

• Recognize overall trends and exceptions.

• Distinguish association from causation.

• Identify unsupported or exaggerated conclusions.

• Choose the strongest available evidence.

Final SAT Strategy: Match the evidence to the exact wording of the claim. The strongest answer is not necessarily the most interesting fact or largest number—it is the evidence that most directly supports or challenges the stated conclusion.