1. solution: according to the formula: D= PH-PL (where d is the discriminant index, PH is the high grouping pass rate and PL is the low grouping pass rate), 27% of the subjects are selected as high grouping and low grouping respectively;

( 120/ 135)-(50/ 135)=0.88-0.37=0.5 1

Because d is above 0.4, the project is very good.

2.

According to the formula r = krxx/[1+(k-1) rxx]. K is the multiple of the topic increase, and rxx is the original reliability.

r = 0.8 * 0.6/[ 1+(0.6- 1)* 0.8]= 0.48/0.68 = 0.70588823