Regression line — Algebra I · Grade 9 or accelerated Grade 8, what it means and where it is taught
The line of best fit computed by a formula rather than by eye.
Taught in Algebra I · Grade 9 or accelerated Grade 8.
Where it is taught
What it rests on
Work through these first if this one does not settle.
- Line of best fit — A straight line summarising a linear pattern in a scatter plot.
Practise this idea
4 questions in the course bank use Regression line, in Bivariate Data & Correlation.
Problem 1
A regression line is y = 4x + 6. For x = 7 the actual value was 30. Find the residual.
Worked answer
-4
Predicted: 4(7) + 6 = 34
30 - 34 = -4
Problem 2
A regression line is y = -2.5x + 80. Predict y when x = 12.
Worked answer
50
-2.5(12) = -30
-30 + 80 = 50
Problem 3
A regression line has a negative slope. What can you say about the sign of r?
Worked answer
negative
Negative slope means negative r
Problem 4
A regression line for score against hours studied is y = 6.5x + 41. A student studies 4 hours and scores 74. Find the residual.
Worked answer
7
Predicted: 6.5(4) + 41 = 67
74 - 67 = 7