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HomeStatisticsRegression Analyzer

Example: Regression Analyzer

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input
Team size: 1 2 3 4 5 6
Story points: 2.5 4.8 5.1 7.9 8.2 10.5
Output
═══ Verdict ═══
✓ The slope is significant: 1.5143 per unit of Team size (p = 0.000539 < α = 0.05)
ℹ Story points = 1.5143 × Team size + 1.2000
ℹ R² = 0.9623 — the line explains 96.2% of the variation in Story points
✓ Residuals show no evidence against normality
✓ Residual spread looks constant across the range of X

═══ Model ═══
Equation: Story points = 1.5143 × Team size + 1.2000
Slope: 1.5143
Slope std error: 0.1498
Slope t(4): 10.1067
Slope p-value: 0.000539
95% CI for slope: 1.0983 to 1.9303
Intercept: 1.2000
Intercept std error: 0.5835
Meaning of slope: each 1-unit rise in Team size goes with a 1.5143 rise in Story points.

═══ Fit Quality ═══
R²: 0.9623
Adjusted R²: 0.9529
Residual standard error: 0.6268 on 4 df
F(1, 4): 102.1455
Model p-value: 0.000539
Residual sum of squares: 1.5714
Total sum of squares: 41.7000
Correlation (r): 0.9810
Sample size: 6
A high R² means the line tracks these points; it does not prove the line is the right shape or that X causes Y.

═══ Residual Behaviour ═══
Mean residual: -1.48e-16 (always ~0 by construction)
Largest standardized residual: 1.026 at point 3 (3.000, 5.100)
Durbin-Watson: 3.714 (near 2 = no autocorrelation, near 0 = positive, near 4 = negative)
Breusch-Pagan LM: 3.71e-29, p = 1.000000
⚠ Residual normality: not testable with n = 6; judge from the histogram and be cautious
✓ No residual beyond 3 standard errors
ℹ Durbin-Watson needs about 12 points before it means anything

═══ Assumptions ═══
Linearity: the true relationship is a straight line (check the residual plot for a curve).
Independence: each observation is unre
…

About Regression Analyzer

Regression Analyzer preview - Statistics tool

Analyze regression models and coefficients. Part of the DevTools Surf developer suite. Browse more tools in the Statistics collection.

Use Cases

  • Analyze which features most strongly predict customer churn from historical data.
  • Model the relationship between ad spend and revenue to estimate marketing ROI.
  • Identify price elasticity by regressing sales volume against price changes.
  • Validate that a linear model is appropriate before applying more complex ML methods.

Tips

  • Check residual plots before trusting R-squared — a high R-squared with non-random residuals means the model misspecifies the relationship.
  • Standardize features (z-score or min-max) before comparing coefficients — raw coefficients are not comparable when features have different scales.
  • Test for multicollinearity using VIF (Variance Inflation Factor) values above 5–10 indicate redundant predictors that destabilize coefficient estimates.

Fun Facts

  • The term 'regression' was coined by Francis Galton in 1886 to describe how extreme parental traits tend to move toward the population average in offspring — 'regression to mediocrity.'
  • Ordinary Least Squares (OLS) regression, the standard linear regression method, was developed independently by Carl Friedrich Gauss (1795) and Adrien-Marie Legendre (1805) — their priority dispute was one of the most famous in mathematics.
  • Linear regression is computationally trivial by modern standards but in 1950 fitting a regression on a 100-variable dataset required months of hand computation; the first computer-assisted regression analyses were performed in the 1950s at Bell Labs.

FAQ

What does R-squared actually mean?
R-squared (coefficient of determination) is the proportion of variance in the dependent variable explained by the model. 0.8 means 80% of variance is explained. It does not indicate whether the model's predictions are accurate in absolute terms.
When should I use logistic regression instead of linear regression?
Use logistic regression when the outcome variable is binary (yes/no, churned/retained). Linear regression applied to binary outcomes can predict probabilities outside [0,1] and is statistically inappropriate.

Related Statistics Tools

A/B Test CalculatorStatistical Significance TesterConfidence Interval CalculatorSample Size CalculatorChi-Square TesterT-Test CalculatorCorrelation AnalyzerDistribution Analyzer
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