7.48(a): 1 point based on correction. 

hw_lect18_1: 2 points; Showing CI include 0 or not; derive corresponding conclusion.

hw_lect18_2: 1 points; Showing CI and conclude there is no evidence that pi_1 does not equal to pi_2

hw_lect19_1: 2 points; based on completion; partial were given. 

7.58: 1 point based on completion.