You are interested explaining student's test scores using student teacher ratios. You have data on 420 students. If the estimated slope coefficient is -2.5 and the estimated intercept is 604. Calculate the upper value for a 95% mean confidence interval for the predicted value of test scores when student teacher ratio is 20 and the mean value of student teacher ratios is 18. The mean squared unexplained is 345.2523 and 420 E(x, -x)? = 1499.5808. i-1