The other common user error is to use a "Line" chart instead of an "XY
(Scatter) chart. This will result in coefficients that are actually wrong,
instead of merely rounded beyond usefulness.
The "Line" chart occurs earlier in the chart-type menu and is misleadingly
named, inviting the obvious (but wrong) interpretation that it has something
to do with whether you want to connect the points by a line. A "Line" chart
is a chart where the x-axis is composed of categories instead of a numeric
scale (unclear how MS got "Line" out of that). If you provide x-axis
information at all, then it is interpreted as category labels, even if the
range solely contains numeric values. If you request a trendline (unclear
why MS supports trends on non-numeric x-values), then the x-values for the
trend are taken to be 1,2,3,... regardless of the actual x-data provided.
Jerry
