Scatter Plots and Correlation

Name: Scatter Plots and Correlation
Author: StemPy Lab

Ten students tell you how long they practise typing and how fast they type.

Put each student on a graph as one dot, and a pattern appears.
Learn to read that pattern for direction, form and strength, to measure it with the correlation coefficient r, and to spot the cases where r gives the wrong picture.

3 lessons, about 1 h 30 min3 simulations10 problems3 practice questionsPython in every lesson

Course outline (3 lessons)

Lesson 1about 30 min
Reading a scatter plot
When we measure two things about each person, each person becomes one dot on a scatter plot. This lesson shows how to draw one, which variable goes on which axis, and the four things to look for: direction, form, strength and outliers.
1 simulation1 practice question1 Python program2 problems
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Lesson 2about 30 min
The correlation coefficient
The correlation coefficient $r$ puts a number on a straight-line pattern. It is always between $-1$ and $1$ : the sign gives the direction and the size gives the strength. This lesson works out $r$ by hand for five points, explains why the formula works, and checks it with Python.
1 simulation1 practice question1 Python program4 problems1 Python lab
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Lesson 3about 30 min
What r cannot see
The correlation coefficient sees only straight lines. A perfect curve can give $r$ near $0$ , and one wrong point can turn a strong $r$ upside down. This lesson shows the cases where $r$ misleads and the habit that protects you: always look at the scatter plot first.
1 simulation1 practice question1 Python program4 problems1 Python lab1 question set1 note
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15 questions · 20 min

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