A wholesaler has recently developed a computerized sales invoicing system. Prior to implementing this system, a manual system was used. The distribution of the number of errors per invoice for the manual system is as follows
Errors per invoice 0 1 2 3 More than 3
Percentage of invoices 87% 8% 3% 1% 1%
After implementation of the computerized system, a random sample of 500 invoice gives the following error distribution:
Error per invoice 0 1 2 3 More than 3
Number of invoices 479 10 8 2 1
a. Show that it is appropriate to carry out a chi-square test using these data.
b. Use the following Excel output to determine whether the error percentages for the computerized system differ from those for the manual system at the 0.5 level of significance. What do you
