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The minimum number of observations required to run a Joinpoint Analysis (using the Grid Search method) is determined by the following formula:
Min. Num. Obs. = (2 * NumObsEnd) + (MaxJP -1) * NumObsBetween + MaxJP
NumObsEnd: The minimum number of observations from a Joinpoint to either end of the data, excluding the first or last Joinpoint if it falls on an observation.
NumObsBetween: The minimum number of observations between two joinpoints, excluding any Joinpoint if it falls on an observation.
MaxJP: The maximum number of joinpoints, determined by subtracting the user defined minimum number of joinpoints from the user defined maximum number of joinpoints.
If you receive an error message stating that there are too few observations to fit the specified model, check these settings on the Method and Parameters tab and adjust them to fit this formula.