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

**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,