Work out a forecast of the dependent variable from a fitted regression and given values of the explanatory variable, and explain what it means
The idea
A prediction plugs forecast values of each independent variable into the estimated equation: Ŷ = b0 + b1X1 + … + bkXk. Use every estimated coefficient, including the intercept and any slope that is not significant, because the equation was estimated with all of them present; dropping a variable means re-estimating the model without it. Watch signs and units, especially negative inputs and variables quoted in percent. Two sources of uncertainty surround the forecast: the error term itself and the sampling error in the coefficients, so the interval widens for inputs far from their sample means. Frequent slips are forgetting the intercept and flipping the sign of a negative input.
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