Line of best fit — Grade 8 Math, what it means and where it is taught
A straight line summarising a linear pattern in a scatter plot.
Taught in Grade 8 Math.
Where it is taught
What it rests on
Work through these first if this one does not settle.
- Scatter plot — A graph of paired data, one dot per case.
What uses it later
This idea is needed for:
- Regression line — The line of best fit computed by a formula rather than by eye.
Practise this idea
3 questions in the course bank use Line of best fit, in Lines of Best Fit.
Problem 1
A line of best fit passes through (0, 12) and (4, 24). Find its equation.
Worked answer
y = 3x + 12
b = 12
m = 24 - 124 = 3
y = 3x + 12
Problem 2
A line of best fit passes through (0, 50) and (10, 30). Find its equation.
Worked answer
y = -2x + 50
b = 50
m = 30 - 5010 = -2
y = -2x + 50
Problem 3
A line of best fit is y = -1.5x + 60. Predict y when x = 12.
Worked answer
42
-1.5(12) = -18
-18 + 60 = 42