Can anyone (briefly) compare and contrast these two Excel features? We have a set of data from a study for which we are trying to plot a decay curve with an accompanying half-life calculation. One option is to create a plot of the data with an exponential trendline (Y=b*exp^cx). Another is to use the Solve add-in, utilizing the same equation, and minimize the sum of the squared deviations by manipulating the regression coefficients (b and c). Both methods seem to yield a curve that gives a reasonable approximation of the observed data, but with slightly different rate coefficients, which will of course yield slightly different half-lives. Any thoughts on which approach is more appropriate? Thanks.