6.3 Command of Evidence: Quantitative

Some Information and Ideas items pair a short text with an informational graphic: a table, a bar graph, or a line graph. College Board includes those displays in the same 12–14 operational Information and Ideas questions as central ideas, textual evidence, and inferences. The skill name is Command of Evidence (quantitative). The job is still matching. The evidence just happens to be numbers in a display rather than a quotation.

This independent OpenExamPrep section helps 8th and 9th graders study those graphics on the PSAT 8/9. OpenExamPrep is not a College Board partner and does not claim official approval, review, or exact equivalence with College Board materials. The tables below are original teaching examples, not official exam items.

You are not being asked to run a statistics unit. Margin of error, sample-to-population inference, and experimental design are not PSAT 8/9 Math testing points, and you should not drag them into these Reading and Writing items. You are being asked to read a title, a unit, and a comparison honestly.

Read the graphic before you read the claim

Treat the display as its own tiny passage:

1. Title. What is being measured, and over what?
2. Units. Centimeters of rain is not the same as days of rain. Kilograms recycled is not the same as percent of waste recycled.
3. Axes or headers. On a bar or line graph, one axis usually shows categories or time; the other shows the measured amount. On a table, column headers do the same job.
4. Legend and categories. If two colors or two rows exist, the claim must point at the correct one.
5. Only then look back at the statement and ask whether the numbers support it, weaken it, or merely illustrate a pattern the text already named.

If you read the claim first and then glance at the tallest bar, you will often attach the claim to the wrong category.

Support, weaken, or illustrate

• Support: The numbers go in the same direction as the statement, for the same group and time the statement names.
• Weaken: The numbers go the opposite direction, or they show a different group is larger than the group the speaker praised.
• Illustrate: The graphic is a picture of a pattern the text describes (summer highs rise then fall) without adding a new cause.

Illustrate is easy to over-read. A line that climbs from week 1 to week 4 illustrates an increase. It does not, by itself, show that a new policy, a celebrity visit, or better weather caused the increase.

Example: a small rainfall table

A middle-school weather station recorded average monthly rainfall in centimeters:

A student writes: At this station, July was drier than May.

That statement is supported. July's 1.3 cm is less than May's 4.4 cm. The table does not support July was drier because a new parking lot was paved in June. No parking-lot variable appears. The table also does not support July was wetter than March: 1.3 is not greater than 8.2. Units are already in centimeters; you do not reject the table because you personally prefer inches.

This is the same claim-first habit as textual evidence, except the hunt is a cell instead of a sentence.

Example: a bar graph of recycling mass

The bar chart with this lesson shows kilograms a middle school recycled in March by material: glass 18, paper 41, plastic 27, metal 12. Read it with the same checklist. The title is about kilograms recycled, not about how students feel about recycling and not about the percent of classroom trash that was diverted.

Which statements do those bars support?

• Paper was the largest of the four materials by mass. Supported (41 is the highest value).
• Metal was the smallest of the four by mass. Supported (12 is the lowest).
• Students care more about paper than about metal. Not supported. Mass is not an attitude survey.
• The school recycled more in March than in February. Not supported. February is not on the chart.
• Banning plastic bottles caused paper to be the largest category. Not supported. No cause is in the display.

A speaker who says metal was the most recycled material is weakened by the bars. That is a quantitative-evidence item in one sentence: the claim names a ranking, the bars show a different ranking.

Example: line-graph data as a table

Line graphs on this exam are usually time on the horizontal axis and a measured amount on the vertical axis. You can read the same information in a table. Average weekday riders on city bus Route 4:

The data support a careful statement: average weekday ridership generally increased from week 1 through week 4, then dipped slightly in week 5. The data do not support free fares caused the rise (no fare variable). They do not support Route 4 was the busiest route in the city (no other routes). They do not support ridership will exceed 500 in week 6 (the table stops at week 5).

If a passage says ridership on Route 4 climbed through the first month of a new schedule, this table can illustrate that climb through week 4. Illustration still does not license a cause the graphic does not measure.

Trap types for quantitative evidence

The invented-cause trap is the one to drill. Science and social-studies classes rightly talk about why patterns happen. This item type does not give you a second study with a control group. If the graphic does not include the cause, you may not credit a choice that invents it—even if the cause sounds plausible from world knowledge.

That limit is the cousin of Inferences: stay with what the information forces, not with what might be true in real life.

A one-minute graphic routine

1. Cover the choices. Read title, units, and headers.
2. Restate the claim as a testable sentence about these numbers.
3. Point to the exact cell, bar, or point the claim needs. Say the number out loud.
4. Ask support, weaken, or illustrate—then ask whether any leftover words in the choice add a cause, a future, or another group.
5. If two choices both seem numerically true, keep the one that does not overclaim.

You do not need Desmos for these Reading and Writing graphics. The calculator belongs to Math. Here the tool is slower eyes: title first, then the comparison.

Information and Ideas graphics appear in the 54-question Reading and Writing section, typically one question per short text-plus-graphic pair. They are still four-choice items. Questions of similar skill are grouped, then ordered from more approachable to more demanding inside a module. Early items may ask which statement the table supports. Later ones may ask which statement the data weaken, which is the same comparison with a negative.

/practice/psat-89Practice questions with detailed explanations

Quick checks before you tap an answer

• Cover the claim and state one sentence the graphic does show. Then uncover the claim and compare.
• Trace the unit from the title into the choice. If the choice switches units, it is probably wrong.
• If a choice uses because, caused, proves, or will, look for that extra idea in the display. If it is missing, drop the choice.
• Tallest is not always the answer. The stem might ask for a decrease, a comparison of two middle bars, or a weakening statement.

Read the numbers. Then stop. That is the whole skill.