1One regression line: The dummy and interaction
coefficients are zero (meaning they’re not statistically
significant).
2Two regression lines with different intercepts but the
same slope: The coefficient for the dummy variable is
significant, but the interaction coefficient is zero (or not
statistically significant).
2Two regression lines with the same intercept but
different slopes: The dummy coefficient is zero (or not
statistically significant), but the interaction coefficient is
significant.
2Two regression lines with different intercepts and
slopes: The dummy coefficient and the interaction coefficient
are both significant.
Figure 9-6 shows a graphical depiction of the resulting
regression with an insignificant dummy coefficient but a
significant interaction coefficient. Note: The dummy
coefficient isn’t significantly different from zero.