Source Analysis and Argumentation: Data, Texts and Reasoned Writing
Domain 8 is skill-based: reading tables, charts and short texts accurately, detecting bias and flawed reasoning, and writing a structured argument.
Quantitative sources
Check title, units, axis scales, base year, and whether figures are nominal or real. Percentage points measure a difference between percentages; percent measures relative change. Watch truncated axes (starting at 50 exaggerates a gap), dual axes, changing categories between years, and missing sample sizes.
Text sources
Identify the thesis, the supporting arguments, and the author's standpoint (date, place, purpose). Separate fact from opinion, description from evaluation. For primary versus secondary sources ask who produced it, for whom, and with what interest; corroborate before relying on it.
Argument structure
Conclusion, premises, hidden assumptions. Tests: validity (does the conclusion follow?), soundness (are the premises true?), relevance. Name fallacies precisely: ad hominem, straw man, false dilemma, slippery slope, post hoc, appeal to authority, hasty generalisation, circular reasoning.
Worked example
A chart shows support for EU membership rising from 80% to 88%, and a commentator writes that support 'rose by 8%'. The statement is imprecise: the rise is 8 percentage points, or about 10% in relative terms. If the sample was 300 respondents from one region while the conclusion concerns the whole country, the argument also commits a hasty generalisation.
Writing
Thesis first; then two or three arguments, each with evidence; then a counterargument that is answered; then a conclusion restating the position. Marking rewards explicit reasoning links ('because', 'therefore') and the use of the source, not slogans.
Traps
- Confusing percentage points with percent - the most frequent lost marks.
- Treating correlation as causation.
- Ignoring the date, author and addressee of a quotation.
- Stating an opinion without supporting evidence from the source.