Grade: Grade 7 Subject: English Language Arts Unit: Analyzing Arguments Lesson: 5 of 6 SAT: Craft+Structure ACT: Reading

Evaluating Evidence

Learn to assess whether evidence effectively supports an argument's claims.

Learn

Strong arguments require strong evidence. In this lesson, you will learn how to evaluate whether the evidence an author uses actually supports their claims. This skill is essential for both reading critically and building your own arguments.

Types of Evidence

  • Facts and Statistics: Numerical data and verifiable information
  • Expert Testimony: Opinions or statements from qualified authorities
  • Examples and Anecdotes: Specific instances that illustrate a point
  • Research Studies: Findings from systematic investigations
  • Primary Sources: Original documents, interviews, or firsthand accounts

Criteria for Evaluating Evidence

  1. Relevance: Does the evidence directly relate to the claim?
  2. Sufficiency: Is there enough evidence to support the claim?
  3. Credibility: Is the source of the evidence trustworthy?
  4. Currency: Is the evidence current and up-to-date?
  5. Accuracy: Can the evidence be verified?

Red Flags in Evidence

  • Vague or unsourced statistics ("Studies show...")
  • Outdated information used for current claims
  • Cherry-picked data that ignores contradicting evidence
  • Anecdotes presented as proof of general trends
  • Appeals to anonymous or unqualified "experts"

Examples

Example 1: Evaluating Statistical Evidence

Claim: "Smartphones are harmful to teenagers."

Evidence: "A 2023 study by researchers at Stanford University found that teens who spend more than 4 hours daily on smartphones report 40% higher rates of anxiety and depression compared to those who use phones less than 1 hour daily."

Analysis

Evaluation: This is strong evidence because:

  • Relevance: Directly addresses smartphone use and teen mental health
  • Credibility: Comes from a reputable university
  • Specificity: Provides specific numbers and comparison groups
  • Currency: Recent study (2023)

However, note that correlation does not prove causation - the study shows association but does not prove smartphones cause mental health issues.

Example 2: Weak Evidence

Claim: "Video games make children violent."

Evidence: "My neighbor's son plays video games all day and he got into a fight at school last week."

Analysis

Evaluation: This is weak evidence because:

  • Sufficiency: One example cannot prove a general claim
  • Causation: No evidence the video games caused the fight
  • Cherry-picking: Ignores millions of gamers who are not violent
  • Type: An anecdote, not systematic research

Practice

Evaluate the evidence in each scenario. Click to check your thinking.

Question 1: A website claims "Organic food is healthier" and cites "a study by researchers." Is this evidence strong or weak? Why?

Answer

Weak evidence. The source is vague ("a study by researchers") with no specifics about who conducted the study, when, or what they measured. Strong evidence would name the institution, publication, and specific findings.

Question 2: To support the claim "Regular exercise improves academic performance," an author cites a 2022 meta-analysis from the Journal of Educational Psychology that reviewed 50 studies involving 12,000 students. Evaluate this evidence.

Answer

Strong evidence. It comes from a peer-reviewed journal, reviews multiple studies (meta-analysis), has a large sample size (12,000 students), and is recent (2022). The breadth of studies reviewed adds to reliability.

Question 3: A politician claims "Crime is out of control" and uses crime statistics from 1995 to support this. What is the problem with this evidence?

Answer

The evidence lacks currency. Statistics from nearly 30 years ago cannot accurately represent current crime rates. To evaluate whether crime is "out of control" today, current data is needed.

Question 4: An advertisement claims their supplement "boosts energy by 200%" based on "doctor recommendations." Evaluate this evidence.

Answer

Weak evidence. "Doctor recommendations" is vague - which doctors? How many? What are their qualifications? The 200% claim needs to be verified through clinical trials, not just recommendations. Advertisements often use misleading statistics.

Question 5: To argue that "Schools should start later," a student cites the American Academy of Pediatrics recommendation that middle and high schools start no earlier than 8:30 AM. Is this good evidence?

Answer

Strong evidence. The American Academy of Pediatrics is a credible, authoritative organization of medical professionals. Their recommendation is based on research about adolescent sleep needs. This is relevant expert testimony.

Question 6: A news article claims "Most Americans support this policy" but only surveyed 50 people at a single shopping mall. Evaluate the evidence.

Answer

Weak evidence due to insufficiency and bias. 50 people cannot represent 330 million Americans. Additionally, people at one shopping mall may not be representative of the general population (sampling bias). A reliable poll would survey thousands through random sampling.

Question 7: To support the claim "Reading improves vocabulary," an author notes that "According to a 2021 study in Reading Research Quarterly, students who read 20+ minutes daily knew an average of 1,800 more vocabulary words than non-readers." Evaluate this.

Answer

Strong evidence. The source is a peer-reviewed academic journal, the study is recent, it provides specific and measurable data (20+ minutes, 1,800 words), and it directly relates to the claim about reading and vocabulary.

Question 8: A company claims their product is "the best" because "9 out of 10 customers recommend it." What questions should you ask about this evidence?

Answer

Questions to ask:

  • How many total customers were surveyed? (9 out of 10 could mean just 10 people)
  • How were customers selected? (Were they paid or only satisfied customers?)
  • Who conducted the survey? (The company itself has bias)
  • What exactly did they "recommend"? (Vague phrasing)

Question 9: A historical essay claims "The Industrial Revolution improved lives" and uses only examples of wealthy factory owners' increased profits. What's missing?

Answer

The evidence is cherry-picked and insufficient. To support a claim about "improved lives" generally, the author needs evidence about different groups: workers, children, families, health outcomes. Focusing only on wealthy owners ignores the experiences of most people affected by industrialization.

Question 10: A blogger claims "Social media causes loneliness" and cites their personal experience of feeling lonely after using Instagram. Is this sufficient evidence?

Answer

Insufficient evidence. A personal anecdote cannot prove a general causal claim. The blogger's experience may not be typical, and many factors could contribute to loneliness. Research studies with control groups would be needed to establish causation.

Check Your Understanding

  1. What are the five criteria for evaluating evidence?
  2. Why is an anecdote usually weaker than statistical evidence?
  3. What makes expert testimony credible?
  4. How can you identify cherry-picked evidence?
  5. Why does correlation not equal causation?

Next Steps

  • Practice evaluating evidence in articles you read
  • Look for the five criteria when reading arguments
  • Continue to the Unit Checkpoint to assess your overall understanding