According to the document, spreadsheet errors are common, with 20-40% of spreadsheets containing errors and 90% of complex spreadsheets containing errors. The main types of errors are logic errors from incorrect assumptions, mechanical errors like typos, and omissions. Common causes of errors include time pressure on projects, overconfidence among developers, and lack of corporate spreadsheet standards. The document recommends techniques like setting development standards, data entry procedures, ballparking estimates, and double checking work to minimize spreadsheet errors.

1. Spreadsheet ErrorsDesigning Financial Models That WorkDmitry Stechny

2. Error RatesConsultants claim that based on practical experience 20-40% of all spreadsheets contain errors

3. Coopers and Lybrand in England found that 90% of all spreadsheets with more than 150 rows contained errors.

4. High error rate in spreadsheets consistent with data on human error rates from other work domainsTypes of ErrorsLogic errors – are errors in fundamental reasoning. Usually caused by incorrect assumptions made at the beginning.

5. Mechanical errors – typically data entry typos and wrong cell references