Polynomial Trendline function flaws in Microsoft Excel

Numerous statistical and graphical problems have been reported for different versions of Microsoft Excel, including the newest version (Excel 2007). We report newly discovered problems with Excel 2007 when generating polynomial trend line equations, having a user-specified (forced) intercept, from graphed data. We also remind users of Excel’s Trendline function of problems with Excel 2003 that have not been corrected in Excel 2007. Excel will “fit” nonsense trend lines to data presented on column and line charts, and can report an inadequate number of significant digits for polynomial trend lines. We provide suggestions for avoiding these continuing problems, but are unable to identify an Excel 2007 workaround solution for the forced-intercept polynomial trend line errors.