Scatter plots and lines of fit – Grade 8 math lesson
Lesson 16 of 16 in the Grade 8 math course
US version. US grades, US spelling and dollars ($). · UK Maths Department
A complete 45-minute lesson for grade 8 (ages 13–14) that runs on this page – at school or at home. Every answer is graded right away, with a worked explanation.
- Time
- 45 minutes + 20 min homework
- Grade
- Grade 8 (ages 13–14)
- You need
- Paper, a pencil and this page
- Graded
- Instantly, with explanations
For parents: how to use this lesson
You don't need to know this topic yourself. The lesson explains each step on screen, one tidy step at a time. Every answer is graded straight away with a worked explanation, so you never have to grade anything.
- Read what your child will learn and the big ideas together.
- Press Start the lesson below and sit with your child for the teaching and the worked examples (about 19 minutes).
- Let them do the practice on their own. They choose Getting started, On track or Challenge – start on On track and move up after a few right in a row.
- Finish with the exit ticket and the talk question: “Does a link between two things mean one causes the other? Think of an example.”
- Later that day or the next day: the homework (20 minutes), then a practice test.
Watch out for
- Joining the points dot to dot. Draw one straight line through the middle of the points.
- Saying correlation means one causes the other. Ice-cream sales and sunburn rise together because of sunny weather.
Tip for home: Talk about whether taller people have bigger feet, and test it.
What your child will learn
Learning goal: plot and interpret scatter plots and use lines of fit.
Success looks like
- I can plot a scatter graph.
- I can describe correlation.
- I can use a line of best fit to estimate.
Key words
- correlation
- a relationship between two variables
- line of fit
- a straight line through the middle of the points
- outlier
- a point far from the pattern
- interpolate
- estimate within the range of the data
What to have ready
- Paper and a pencil
- This page on a computer, tablet or phone
- For the hands-on part: Measure hand spans and heights of family members and plot them on a scatter graph.
The big ideas (for the adult)
A scatter graph plots pairs of values to see if they are related.
Positive correlation: as one goes up, so does the other. Negative: as one goes up, the other goes down. No correlation: no pattern.
A line of fit follows the trend of the points. Use it to estimate, but only within the range of the data. Correlation does not prove one thing causes the other.
The lesson, step by step
| Part | Time | How it is checked |
|---|---|---|
| Starter: quick recall | 5 min | Graded by Classfern |
| Teaching input | 10 min | Not assessed, self-checked |
| Worked examples and guided practice | 9 min | Not assessed, graded by Classfern |
| Independent practice | 15 min | Graded by Classfern |
| Closure and exit ticket | 6 min | Graded by Classfern, self-checked |
Starter, "your turn", practice and exit ticket are graded by Classfern. Worked examples and teaching are not assessed. The hands-on task and the reflection are self-assessed. Explanations in talk are judged by the parent and not recorded.
The lesson
It runs here on the page. No sign-up and no names – progress is kept only in this browser.
Homework and practice at home
20 minutes: 10 practice questions, 3 multiple-choice questions and 2 to remember from earlier work, then a short reflection. New questions every time, all graded instantly.
More practice
More Grade 8 math lessons
- Repeating decimals
- Scientific notation
- Laws of exponents
- Square roots and cube roots
- Simplifying expressions
- Solving equations
- Systems of equations
- Arithmetic and geometric sequences
- Linear functions and slope
- Functions
- Graphing functions
- Angle relationships
- Volume and surface area
- The Pythagorean theorem
- Transformations
Curriculum
Common Core State Standards 8.SP.A.3: “Use the equation of a linear model to solve problems in the context of bivariate measurement data, interpreting the slope and intercept. For example, in a linear model for a biology experiment, interpret a slope of 1.5 cm/hr as meaning that an additional hour of sunlight each day is associated with an additional 1.5 cm in mature plant height.”
Common Core State Standards 8.SP.A.1: “Construct and interpret scatter plots for bivariate measurement data to investigate patterns of association between two quantities. Describe patterns such as clustering, outliers, positive or negative association, linear association, and nonlinear association.”
Our lessons and questions are our own. They are not written or endorsed by any government department, testing agency or exam board.