You have fit a regression model. The predictor x has a p-value < 0.0001. The p-value for x2 is 0.07. The p-value for x3 is 0.025. The p-value for x4 is 0.083. If a = 0.05, which predictors should be included in your model?
1) x2, x3, x4
2) x, x3
3) x2, x3
4) x, x2, x3, x4