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Auralith Learning

Year 8 · Maths · Representing data · Lesson 3

Lines of best fit

Learn to draw a line of best fit on a scatter graph, use it to estimate values in both directions, choose the best line, ignore outliers, and judge when an estimate is reliable.

Whiteboard video lesson: Lines of best fit

26-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

  • Draw a line of best fit
  • Use a line of best fit to estimate values
  • Choose the best line of best fit
  • Ignore outliers when drawing the line
  • Decide when an estimate is reliable

The method

  1. Draw one straight line with a ruler.
  2. Follow the trend, through the middle of the points.
  3. Ignore outliers.
  4. Read estimates from the line, inside the data range.

Key words: line of best fit, trend, estimate, outlier, reliable.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

Draw a line of best fit on the scatter graph.

  1. Step 1: Look at the trend
  2. Step 2: Follow the trend of the points.
  3. Step 3: About the same above (6) and below (1).

Answer: A straight line through the middle of the points

Question 2

Draw a line of best fit on the scatter graph.

  1. Step 1: Look at the trend
  2. Step 2: Follow the trend of the points.
  3. Step 3: About the same above (4) and below (0).

Answer: A straight line through the middle of the points

Question 3

Draw a line of best fit on the scatter graph.

  1. Step 1: Look at the trend
  2. Step 2: Follow the trend of the points.
  3. Step 3: About the same above (5) and below (1).

Answer: A straight line through the middle of the points