Google Spreadsheet Add-on for Classical Item and Test Analysis
This add-on allows you to quickly generate all the Classical Item and Test Analysis statistics, reports and charts easily with only a few clicks.

With add-on you can easily perform complete item analysis procedure and  evaluate the quality of exams. The add-on computes both item and test level statistics. Some of these statistics are listed below:

Mode
Median
Mean
Std.Dev.
Variance
Skew
Kurtosis
KR-20
SEM
Difficulty Index 
Discrimination Index