Weighted average trend analysis
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You can perform a weighted average trend analysis to incorporate knowledge learned from fitting the same trend model to prior data in order to obtain an "improved" fit to the present data. The smoothed trend line combines prior and new information in much the same way that exponential smoothing works. In a sense, this smoothing of the coefficients filters out some of the noise from the model parameters estimated in successive cycles.

If you supply coefficients from a prior trend analysis fit, Minitab performs a weighted trend analysis. If the weight for a particular coefficient is a, Minitab estimates the new coefficient by:

a p1 + (1 - a) p2, where p1 is the coefficient estimated from the current data and p2 is the prior coefficient.