Three Sources on a Wind Farm
Grade 9 students investigate a proposed 60-turbine wind farm in a rural county. They have three sources.
Source 1 - developer's fact sheet: « 400 jobs created; $2 million per year in municipal tax revenue; clean energy for 90,000 homes. » No dates, methods, or definitions are given.
Source 2 - citizens' group open letter: « Turbines cause sleep loss and destroy property values. Our county will never be the same. » No figures are cited.
Source 3 - provincial report: measured night-time noise at three operating wind farms (38–42 dB at 500 m), plus a 2019 study of property sales near one wind farm in a different region that found no measurable effect on sale prices.
The class must answer: « What are the likely economic effects of the wind farm on the county? »
1. Rank the three sources for usefulness in answering this specific question, and justify the ranking, including the limits of each.
Read the worked answer
1st - Source 3. It is the only source with methods, measurements, and a stated comparison. But it is limited in two ways: the property study comes from another region, so it may not transfer to this county's housing market, and noise data speak to health and annoyance, not directly to economics.
2nd - Source 1. It supplies the only direct economic figures (jobs, tax revenue), which the question actually asks about. Its limits are severe: « 400 jobs » is undated and probably counts construction only; it does not say how many go to county residents; « $2 million » does not say whether it is gross or net of provincial requisitions. Figures exist, but they are not yet usable.
3rd - Source 2. For the economic question it offers no figures and no method, so it cannot answer the question. That does not make it worthless: it identifies an effect worth checking (property values) and shows what residents fear, which is itself part of the story.
Key move: rank by fit to the question asked, not by how likeable or trustworthy the source feels.
2. Name two pieces of information the class still needs before writing a conclusion, and say which source should have supplied each.
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Accept any two well-argued items, for example:
- The split between construction jobs and permanent jobs, and the share going to county residents. Source 1 should have given this; without it « 400 jobs » may describe a two-year boom, not a lasting economic effect.
- Property sales data from this county, before and after construction. Source 3 studied a different region; Source 2 asserts an effect without evidence. Neither gives local numbers.
Other defensible items:
- Whether the $2 million is gross tax revenue or net after provincial requisition (Source 1).
- Costs the county absorbs: road upgrades, emergency services, decommissioning.
- Whether the noise measurements apply to this terrain and turbine spacing (Source 3).
A complete answer notes that every gap traces back to a source's missing method or missing scope, not simply to "bias."
3. A student writes: « Source 2 is biased, so it tells us nothing. » Critique this reasoning.
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The reasoning confuses bias with irrelevance.
- Bias affects how a claim is framed and weighted; it does not mean the underlying event is invented. Source 2 points to a real, checkable effect - property values - that can be tested with sales records.
- The correct response to an interested source is to test the claim, not discard it: what evidence would we need to see to believe this, and does it exist?
- The criticism is also inconsistently applied. Source 1 is equally interested - it is written by the developer - yet the student treats it as neutral information.
Reliability is not a fixed property of a source; it is a judgement about a specific claim. A developer's fact sheet may be the best available source for the number of turbines and the worst for whether the project is a good idea. The student should ask, for each claim: who produced this, for what purpose, and what would confirm it?