A main purpose of applying the multiple regression analysis is to show that certain variables are significant factors for the dependent variable of our interest. With a given dataset, however, we sometimes obtain an insignificant estimate for an explanatory variable. Below is one possible comment on such insignificant estimation results. It is expected that a more sophisticated model with more observations in the sample could produce more significant results. (a) A more sophisticated model would be an extended one which includes more relevant variables. Explain why such an extended model could yield significant results. (b) A more sophisticated model could also be obtained by deleting irrelevant variables. Explain why it is better to delete weakly significant variables which are not of our interest and get little support from theory and previous studies. Explain why more observations would increase the significance