The Scientific Method — Reference Sheet

Key concepts from Week 1. Keep this handy throughout the module.

The cycle

Observation → Question → Hypothesis → Prediction → Test → Revise
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Science is not a body of facts — it is a process for reducing uncertainty. The cycle never really ends: revised hypotheses generate new predictions, which get tested, which lead to further revisions.

Reasoning types

Type	Direction	Example
Deductive	General → specific	“If biomass is carbon-neutral, we predict zero net CO₂ over a growth cycle.”
Inductive	Specific → general	“We observe that forests take 40+ years to regrow, so biomass may not be carbon-neutral on policy timescales.”

Deduction tells you what should follow from a theory. Induction tells you what the evidence suggests. Good science uses both — but deduction is where testable predictions come from.

Testable hypotheses

A hypothesis is testable if you can specify what evidence would disprove it. If no observation could ever show it wrong, it isn’t a scientific hypothesis.

Statement	Testable?	Why?
“The Earth is 6,000 years old.”	Yes	Radiometric dating, geological evidence, and cosmological observations can (and do) contradict this.
“Wind farms reduce bird populations.”	Yes	Compare bird counts near wind farms to control sites before and after construction.
“Renewable energy is the right thing to do.”	No	This is a value judgement, not a factual claim. No measurement can confirm or refute it.
“Burning biomass is carbon-neutral.”	Depends	As stated, it’s vague. Over what timescale? Including what costs? Once you define the terms precisely, it becomes testable.

If your hypothesis isn’t testable, sharpen it until it is.

Falsifiability (Popper)

We can never prove a theory is true — only fail to disprove it.
A single counterexample can overturn a theory, but a thousand confirmations can’t prove it forever.
Confirmation bias makes us seek evidence for what we already believe. The scientific method forces us to look for evidence against it.

The Wason selection task — a reminder

You were shown four cards and a rule. Most people instinctively check the cards that could confirm the rule, not the ones that could falsify it.

This isn’t a personal failure — it’s a universal cognitive bias. The whole point of the scientific method is to protect us from it by making disconfirmation systematic.

Questions to carry forward

These will recur throughout the module:

Question	First appears	What it checks
“Is that a big number?”	Week 2	Context and comparison
“Compared to what?”	Week 2	Control and baseline
“What assumptions are we making?”	Week 3	Hidden premises
“How plausible was this before we tested?”	Week 6	Prior probability / base rate
“What is the model not capturing?”	Week 8	Model limitations

You don’t need to understand all of these yet. By Week 10, they should be reflexes.