Confidence intervals and Significance Tests for Correlation and Regression (2 of 5)

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Regression Slope

Confidence Interval
A confidence interval on the slope of the regression line can be computed based on the standard error of the slope (b). The formula for the standard error of b is:



where s_b is the standard error of the slope, s_est is the standard error of the estimate, and X_M is the mean of the predictor variable. The formula for the standard error of the estimate is:



for the example data for which S_y = 2.432,

.

The only remaining term of needed to be computed is:

Σ(X - X_M)² = (2-4.833)² + (3-4.833)² + ... + (9-4.833)² = 30.833.

Therefore,