Coefficients:
            Estimate Std. Error t value Pr(>|t|)
(Intercept)  -0.2265     1.3192  -0.172   0.8659
X          -0.6510     0.3547  -1.835   0.0864

Coefficients:
            Estimate Std. Error t value Pr(>|t|)
(Intercept)   -4.416      6.001  -0.736    0.475
X            1.365      2.135   0.639    0.534
Z            7.756      9.591   0.809    0.433
X:Z       -3.281      3.317  -0.989    0.341