QUB | Archaeology and Palaeoecology | The 14Chrono Centre

Manual for psimpoll and pscomb

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Menu M: data analyses

Menu Me: correspondence analysis
Menu Meb: Downweighting of rare types
This option enables a transformation that gives rare types a lower value, reducing their significance in the analysis. All values for a taxon are reduced if the overall level of the frequency if the taxon is less than 0.2 times the overall frequency of the most abundant taxon. The measure of frequency used here is the square of the sum of all the values for the taxon divided by the sum of the squares of the values.

This option toggles `on' and 'off'.

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