A wholesaler has recently developed a computerized sales invoicing system. Prior to implementing this system, a manual system was used. Historically, the manual system produced 87% of invoices with 0 errors, 8% of invoices with 1 error, 3% of invoices with 2 errors, 1% of invoices with 3 errors, and 1% of invoices with more than 3 errors. After implementation of the computerized system, a random sample of 500 invoices showed 479 invoices with 0 errors, 10 in-voices with 1 error, 8 invoices with 2 errors, 2 invoices with 3 errors, and 1 invoice with more than 3 errors.
a. Show that it is appropriate to carry out a chi-square test using these data.
b. Show how the expected frequencies (the Eis) on the partial Excel output in the page margin have been calculated.