Does more sleep mean quicker reactions? Do taller people read better? Two numbers measured for the same person make a pair, and a scatter graph lets you see whether the pairs follow a pattern. This unit starts with plotting and describing that pattern, then fits a line of best fit through the mean point and uses it to predict, carefully. After that comes r, one number that measures how closely dots follow a straight line, and what a single odd dot can do to it. The last lesson asks the question that matters most: when two things move together, does one cause the other, and was the data collected fairly?
No lesson needs a calculator beyond the four operations; r is read from technology, not worked out by hand. Never a graphic display calculator.
The lessons, in order
- Lesson 1 · Two numbers, one dot: plotting pairs Bivariate data, independent and dependent variables, plotting pairs and the direction of a scatter graph. Add pairs of sleep hours and reaction times one at a time and watch the dots appear. No calculator
- Lesson 2 · Direction, form and strength Direction, form and strength of correlation, and what an outlier is. Choose a shape and a spread and read the three-word description. No calculator
- Lesson 3 · The line of best fit and the mean point The mean point, drawing a line of best fit by eye, and what makes a line fit well. Turn a line about the mean point and watch the gaps above and below. No calculator
- Lesson 4 · The equation of the line, and predicting Gradient and intercept of a line of best fit, predicting, and interpolation against extrapolation. Choose an age and see whether the line's height is a reasonable prediction. No calculator
- Lesson 5 · r: one number for strength The meaning of r from −1 to 1, a rough guide to strength, and the effect of an outlier on r and on the line. Move a ninth dot and watch r and the slope of the line change. No calculator
- Lesson 6 · Does one cause the other? Lurking variables and bias Correlation and causation, lurking variables, and bias and reliability in how data are collected. Colour ten children's dots by age and see the link disappear inside each age group. No calculator
Every lesson has a teacher page with the answers, the misconceptions each wrong answer reveals, discussion questions, differentiation and support for students learning in English, and extra questions in three tiers.