Final answer:
The estimated marginal effect of x on y in the model yhat = 5 + 3 × x is 3. This means for every one-unit increase in x, yhat increases by 3 units, regardless of the specific value of x.
Step-by-step explanation:
The estimated marginal effect of x on y in the model yhat = 5 + 3 × x is the coefficient of x, which is 3.
This means that for each one-unit increase in x, yhat (the predicted value of y) is expected to increase by 3 units.
When x = 2, the particular value of x does not change the marginal effect, as it is constant in a linear model.
Therefore, the estimated marginal effect of x on y when x=2 is still 3.