The F-test evaluates the overall fit of the model. To examine the individual model components, we can use the t-ratio associated with each estimated coefficient. Under the null hypothesis for each explanatory variable, the coefficient equals zero and does not affect GDP growth. A t-ratio that is relatively large in absolute value indicates that the coefficient is likely different from zero, and the p-value measures the size of this relative magnitude. In particular, we should reject the null hypothesis and conclude that the coefficient is non-zero if the p-value is less than 0.10. Based on the p-values in the GRETL output, which explanatory variables in the base model are not significantly different from zero (i. e., have p-values larger than 0.10)? Based on our study of economic growth, do any of these findings surprise you?