Nonstandard operator precedence in Excel

Microsoft's Excel spreadsheet program implements an unusual operator precedence in formulas. This can cause errors in statistical calculations, if it is not properly followed. For example, some errors by Excel in nonlinear regression reported by McCullough and Wilson (2002. On the accuracy of statistical procedures in Microsoft Excel 2000 and Excel XP. Comput. Statist. Data Anal. 40, 713–721) were probably due to programming by the users that did not follow the unusual operator precedence rules. In this note the operator precedence in Excel is explained, the previous nonlinear regression results are corrected, and a simple example of maximum likelihood estimation is given.