Explain the role of the denominator, Σ(xi - x̄)², in the standard error of the regression slope formula.

The denominator, Σ(xi - x̄)², represents the sum of squared deviations of the independent variable (x) values from their mean. A larger denominator indicates greater variability in x, which often leads to a smaller standard error of the slope, as more variation in x helps in more accurately estimating the slope.