The errors in the inventory records of a company were analyzed for their causes. The findings were 164 cases of omissions, 103 cases of wrong quantity entered, 45 cases of wrong part numbers entered, 24 cases of wrong dates entered, and 8 cases of withdrawal versus deposit mixup. Draw a Pareto diagram for the different causes.

a. What percentage of the cases is covered by the top two causes?

b. If at least 90% of the cases are to be covered, which causes must be addressed?