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📅 Exam
4 to 5 Nov 2026
Home › Data Analysis
Unit 3

📊 Data Analysis

Reading patterns in data, finding relationships between variables, and predicting trends over time. A heavy exam topic, scatterplots, regression lines, time series graphs and seasonal indices all come up every year.

5 subtopics
Appears every exam year
Calculator skills essential
New to Data Analysis? Start with Scatterplots & Correlation, everything else builds on being able to read a scatterplot and describe a relationship. The regression line and time series topics follow naturally from there.
Bivariate Data
1
Ready ✓
Scatterplots & Correlation
Plot two variables against each other and describe the relationship. Is it strong? Weak? Positive? Negative? Linear? How to find and interpret Pearson's r.
explanatory variable response variable Pearson's r strength & direction outliers
Study now →
2
Ready ✓
Least-Squares Regression
Draw the line of best fit, write its equation, interpret the slope and intercept, and use it to make predictions. Know when predictions are reliable (interpolation vs extrapolation).
ŷ = a + bx slope interpretation y-intercept interpolation extrapolation
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3
Ready ✓
Residuals & Residual Plots
Check whether a linear model is actually a good fit. Calculate residuals (actual − predicted) and read a residual plot to spot patterns that suggest a non-linear relationship.
residual = actual − predicted residual plot random scatter = good fit outliers in residual plots
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Time Series Analysis
4
Ready ✓
Time Series & Moving Averages
Data collected over time, spot the trend, smooth out the noise with moving averages, and describe what's happening. 3-point and 4-point moving averages both come up.
trend seasonal variation moving averages centred averages smoothing
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5
Ready ✓
Seasonal Indices
Measure how much a season differs from the annual average. Deseasonalise data to reveal the true trend, then use seasonal indices to make adjusted forecasts.
seasonal index SIs sum to 4 deseasonalise ÷ SI forecast × SI
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Test Yourself, Escape Rooms
⚽
The Transfer Window
Pearson's r · regression equations · residuals · simultaneous equations. Help Coastal FC sign their striker before the deadline.
Play →
🌊
Beach Report
Regression predictions · slope interpretation · extrapolation · r² · residuals. Help the council plan the summer lifeguard roster.
Play →
🎬
Director's Cut
Residuals · negative residuals · outliers · residual plot interpretation. Verify a film studio's analytics report before a $50M deal is signed.
Play →
☕
Second Cup
4-point moving averages · centring · trend interpretation · arithmetic MA patterns. Help Maria decide whether to expand her coastal café.
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🌅
The Forecast
Seasonal indices · sum rule · deseasonalising · forecasting · interpreting SI values. Submit the resort's staffing plan before midnight.
Play →