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L6: Correlation

Revision and practice on using correlation to predict demand and spot patterns in buyer behaviour.

Key vocabulary: Positive Correlation, Negative Correlation, Strong/Weak Correlation

Key Concepts

What Is Correlation?

Correlation looks at the strength of a relationship between two variables. Marketing data may help a business identify a correlation between different factors and demand for a product — for example, comparing sales against price.

Types of Correlation

Positive correlation: as the independent variable increases in value, so does the dependent variable (e.g. as temperature rises, ice cream sales rise).

Negative correlation: as the independent variable increases in value, the dependent variable falls (e.g. as price rises, sales fall).

No correlation: there is no discernible relationship between the two variables.

Strong or Weak Correlation

A line of best fit is drawn through plotted data points to indicate the strength of a correlation.

  • Strong correlation: data points sit close to the line of best fit.
  • Weak correlation: data points are spread widely, further from the line.

If data suggests a strong correlation, the relationship might be used to help make marketing predictions.

Using Correlation — and Its Limits

A business can use a strong, reliable correlation to help forecast demand and inform marketing decisions — for example, spotting that sales rise with advertising spend, or predicting when to stock a seasonal product. But correlation is not the same as causation — just because two variables move together doesn't prove one causes the other. A third, unseen factor might be driving both, and relationships that held in the past may not continue to hold in future, so correlation should always be treated as one input into a decision, not a guarantee.

Real-World Case Studies

UK weather and ice cream sales — a textbook positive correlation

In late June 2026, as average UK temperatures hit around 26°C during a heatwave, ice cream value sales rocketed by nearly 88% in a single week compared to the equivalent period, with volume sales up over 93%. Retailers reported a similar pattern across other summer categories — Tesco's paddling pool sales multiplied fourteen-fold and inflatable sprinkler sales rose by over 1,500% during the same warm spell. This is about as clear a positive correlation as retail data gets: as the "independent variable" (temperature) rises, the "dependent variable" (sales of warm-weather products) rises sharply alongside it.

Source: verified via search, September 2026 — The Grocer and Wholesale Manager coverage of the June 2026 UK heatwave's impact on retail sales.

Why correlation isn't causation — a caution for marketers

Retail analysts studying weather-linked sales data are careful to note that a correlation between two variables (like temperature and ice cream sales) doesn't by itself prove one directly causes the other in every case — other factors, such as school holidays falling at the same time as a heatwave, or a promotional campaign timed for summer, could also be contributing to the same sales spike. This is exactly why AQA Business expects students to treat a strong correlation as useful evidence for a marketing decision, not as absolute proof on its own.

Source: this reflects standard statistical reasoning (correlation vs causation) referenced across UK retail-weather sales reporting, rather than a single specific study.

Matching Activity

Tap a term, then tap its matching description.

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Quick Knowledge Check

Short, snappy recall questions — tap to reveal the answer.

What does a negative correlation show? (1 mark)

As the independent variable increases, the dependent variable falls.

What tells you whether a correlation is strong or weak? (1 mark)

How close the data points sit to the line of best fit.

Why is correlation not the same as causation? (2 marks)

Two variables moving together doesn't prove one causes the other — a third factor might be driving both, or it could be coincidence.

Key Term Flashcards

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Tap a card to flip it, then rate yourself.

Positive Correlation
As the independent variable rises, the dependent variable also rises.
Negative Correlation
As the independent variable rises, the dependent variable falls.
Line of Best Fit
A line drawn through scattered data points to show the general trend — how close points sit to it shows how strong the correlation is.
Independent Variable
The factor being changed or compared (e.g. advertising spend) — plotted on the x-axis of a scatter graph.

A*/A Stretch

Common misconception

"Strong correlation" doesn't mean "certain" — it means the historical data fits the pattern closely. A strong correlation can still break down if external conditions change (a competitor enters the market, the economy shifts, or consumer tastes move on), so forecasts based on correlation should always be treated as a starting point, not a guarantee.

Examiner's eye

Top-band evaluation on correlation questions usually raises the causation issue explicitly — e.g. "although ice cream sales correlate strongly with temperature, this doesn't prove temperature alone causes the sales rise; a heatwave might also coincide with school holidays, boosting footfall for other reasons."

Try This With AI

Before using this: AI tools can get facts or mark scheme details wrong, and quality varies by tool. Always check anything factual against your notes or ask your teacher.

Describe a short business scenario with two variables that might be correlated (e.g. advertising spend and sales). Ask me to say whether I'd expect positive, negative or no correlation, and to explain one limitation of relying on that correlation for a marketing decision. Then mark my answer.