In a linear model, which quantity represents the change in the predicted outcome per unit increase in a predictor, holding others constant?

• A. Intercept
• B. Slope (coefficient)
• C. Residual
• D. P-value

Answer: (B)

The change in the predicted outcome for a one-unit increase in a predictor, while other predictors are held fixed, is given by the slope for that predictor—the coefficient in the linear model. This coefficient tells you how much ŷ changes per unit increase in that predictor when all other variables stay the same. For example, if the slope is 2, increasing the predictor by one unit raises the predicted y by 2 units, assuming the other predictors don’t change. The intercept sets the baseline when predictors are zero, the residual is the prediction error, and the p-value tests whether the coefficient is statistically different from zero.