Unit 2 · Topic 2.4

2.4 Is the evidence enough?

Evidence is sufficient when there's enough of it, and it's strong enough, to support the claim. A big claim needs more and better support than a narrow one, and weak, outdated or one-sided evidence can make readers doubt the whole argument.

Key terms

sufficient evidence
relevant evidence
credibility
bias

Quantity and quality

Sufficient evidence has two parts. Quantity: is there enough of it to support a claim this size? Quality: is each piece relevant, accurate and trustworthy? A pile of weak evidence isn't sufficient, and neither is one perfect example asked to carry a sweeping claim.

Quality checks

Credibility gets extra attention on the synthesis essay, where each source comes with a short description of who wrote it and where it appeared. A study from a research group, an opinion piece by an interested party and a company's advertisement can all be useful, but not in the same way, and Unit 6 covers how to weigh them. Whatever the source, check whether it actually says what you need it to say.

Relevant: does it actually connect to this claim, not just the general topic?
Specific: does it name people, places, numbers or details, or is it vague?
Credible: who produced it, and do they have the knowledge and fairness to be trusted?
Current: is it recent enough for the question? Data on teen phone use from 2005 tells you little about today.
Representative: does it reflect the usual case, or is it an unusual exception?
Accurate: is it quoted or reported correctly, without stretching what it says?

Match the size of the claim to the evidence

How much evidence is enough depends on how much the claim promises. "Some students at my school would use a later bus" needs little support. "Every school in the country should change its bus schedule" needs a great deal. When evidence falls short, you have two honest options: find more and better evidence, or narrow the claim until the evidence you have can carry it. Qualifying a claim this way is covered in Unit 7.

Variety helps too. Three anecdotes about the same kind of person are weaker than an anecdote, a statistic and an expert's view that all point the same way.

When evidence fails

Insufficient evidence costs a writer twice. The claim isn't proven, and readers start to doubt the writer's judgment, so even the good parts of the argument lose force. That's why reading questions sometimes ask which added detail would most strengthen a paragraph, or what a writer's evidence fails to show.

Worked examples

Try each one yourself first, then open the solution.

Example 1
Diagnosing and fixing insufficient evidence
Practice draft (written for this page; the survey is invented for practice): "Phones should be banned in every classroom in America. Last week, my friend got a text during a quiz and lost focus. Clearly, phones destroy students' learning." Explain why the evidence is insufficient, then revise the paragraph so the claim and evidence match.
Show the solutionHide the solution
1. Step 1: Measure the claim: "every classroom in America" and "destroy" make it enormous.
2. Step 2: Measure the evidence: one anecdote about one student on one day. It's relevant, but it isn't representative, and it's far too little for a national claim.
3. Step 3: Choose a fix. Narrow the claim to the writer's own school, and add different kinds of evidence a student could actually gather, such as a class survey and a teacher's observation.
4. Step 4: Keep the anecdote, but let it illustrate a pattern rather than stand in for proof.
Answer: Revised paragraph: Our school should require phones to stay in lockers during class. In a survey our class ran of 120 students (practice data, written for this page), 71 said they check their phones at least once during a typical lesson. Ms. Ortiz, who teaches chemistry, says she now spends the first minutes of each lab collecting phones so students will follow safety steps. My friend's experience shows what those numbers look like: a single text during last week's quiz pulled her attention away for the rest of the period. A narrower claim, backed by a survey, a teacher's view and an example, gives readers far more reason to agree than one story asked to prove a national rule.

Common mistakes

Thinking more quotations automatically means stronger evidence. Three weak quotations are still weak.
Using only one kind of evidence, such as only personal stories, for a broad claim.
Leaving the claim huge when the evidence is small. Narrowing the claim is often the smartest fix.
Ignoring the date or source of evidence, especially statistics.

On the exam

Writing questions may ask whether a writer should add or delete a sentence and why. Choose the answer that names what the evidence does or fails to do for the claim.
In all three essays, the top of Row B requires specific evidence that supports all of your claims. A paragraph with a claim and no real evidence pulls your score down.

Connected topics

Videos

Evaluating a source’s reasoning and evidence | Reading | Khan Academy
Khan AcademyWatch on YouTube (opens in a new tab)
Evaluating Evidence: Crash Course Navigating Digital Information #6
CrashCourseWatch on YouTube (opens in a new tab)
Evaluating Arguments – How to Spot Strong and Weak Claims
Chorus Educational K-12 ContentWatch on YouTube (opens in a new tab)
Evaluating Arguments
Bozeman ScienceWatch on YouTube (opens in a new tab)

Check yourself

4 questions on 2.4 Is the evidence enough?. Pick an answer to see if you got it, and why.

(1) Across the country, more high schools are adding community service hours to their graduation requirements. (2) Some students see the hours as a chore to check off, while others discover causes they care about for years. (3) Community service is a requirement at many schools.

(4) Required service exposes students to problems they might never otherwise see. (5) When I volunteered at the Eastside food pantry for my sophomore hours, I met families who worked full time and still could not afford groceries. (6) That experience changed how I think about hunger in my own town.

(7) Still, a requirement only works if students have real choices. (8) A student forced to file papers in an office for twenty hours learns little except how to watch the clock. (9) Schools that let students pick from many kinds of projects, including ones they design themselves, see more students keep volunteering after graduation.

Written for this practice set: a student's draft of an argument essay answering the question, "Should high schools require community service for graduation?"

Question 1 of 4

A reader might say that paragraph 2 rests on a single experience. Which addition would best address this concern?

Question 2 of 4

The writer wants to make sentence 9 more convincing. Which revision best accomplishes this goal?

After considering the historic page, and viewing the living world with anxious solicitude, the most melancholy emotions of sorrowful indignation have depressed my spirits, and I have sighed when obliged to confess, that either nature has made a great difference between man and man, or that the civilization, which has hitherto taken place in the world, has been very partial. I have turned over various books written on the subject of education, and patiently observed the conduct of parents and the management of schools; but what has been the result? a profound conviction, that the neglected education of my fellow creatures is the grand source of the misery I deplore; and that women in particular, are rendered weak and wretched by a variety of concurring causes, originating from one hasty conclusion. The conduct and manners of women, in fact, evidently prove, that their minds are not in a healthy state; for, like the flowers that are planted in too rich a soil, strength and usefulness are sacrificed to beauty; and the flaunting leaves, after having pleased a fastidious eye, fade, disregarded on the stalk, long before the season when they ought to have arrived at maturity. One cause of this barren blooming I attribute to a false system of education, gathered from the books written on this subject by men, who, considering females rather as women than human creatures, have been more anxious to make them alluring mistresses than rational wives; and the understanding of the sex has been so bubbled by this specious homage, that the civilized women of the present century, with a few exceptions, are only anxious to inspire love, when they ought to cherish a nobler ambition, and by their abilities and virtues exact respect.

I am aware of an obvious inference: from every quarter have I heard exclamations against masculine women; but where are they to be found? If, by this appellation, men mean to inveigh against their ardour in hunting, shooting, and gaming, I shall most cordially join in the cry; but if it be, against the imitation of manly virtues, or, more properly speaking, the attainment of those talents and virtues, the exercise of which ennobles the human character, and which raise females in the scale of animal being, when they are comprehensively termed mankind—all those who view them with a philosophical eye must, I should think, wish with me, that they may every day grow more and more masculine.

Mary Wollstonecraft, an English writer and teacher, A Vindication of the Rights of Woman (1792), from the introduction. Many popular books of the time, most of them written by men, advised that girls be educated mainly to please. Some text is omitted between paragraphs 1 and 2.

Question 3 of 4

Wollstonecraft supports her conclusion in paragraph 1 mainly with

Question 4 of 4

A skeptical reader might argue that the evidence in paragraph 1 is not sufficient because it

0 of 4 answered