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Linear regression calculator
Paste matching x and y values (same order, same count). You get the fitted line, the statistics and a plot.
Formulas
Read more: Linear regression guide · Regression in DMAIC · t table
FAQ
What does R² mean?
The share of the variation in y that the straight line explains. R² = 0.9 means 90% of the variation in y moves with x. It does not prove that x causes y, and a high R² can still hide a curve: always look at the residuals.
How do I know if the slope is significant?
Test H₀: slope = 0 with t = b₁ / SE(b₁) and n − 2 degrees of freedom. A small p-value means the data give evidence of a linear relationship.
What are residuals for?
A residual is the actual y minus the fitted y. If the line fits, residuals scatter randomly around zero. A curve, a funnel shape or a trend over time means the straight-line model is missing something.
Correlation or regression?
Correlation (r) measures how tightly two variables move together, with no direction. Regression fits an equation that predicts y from x, and depends on which variable you call y.
Can I predict outside my data range?
Be careful. The line is supported only between the smallest and largest x you measured. Extrapolating assumes the relationship stays straight where you have no data.
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