QUB |
Archaeology and Palaeoecology |
The 14Chrono Centre
Manual for psimpoll and pscomb
Menu
Most types in a typical full pollen dataset occur
at low frequencies, contributing little that is statistically-useful
(Birks & Berglund 1979). It is
customary, therefore, to limit datasets to those types that reach
a certain minimum value somewhere within the sequence. This option enables you
to select what that value should be. For proportional data, 0.05 (= 5%)
is set as a default. No default is set for other data types. If the value is
negative, the interactive selection of types to include in analyses is
disabled. Use a very small negative number to include everything without
being asked (e.g., -0.00001). Note that if the recalculation option is set
on (menu Mj), the
dataset used in analyses will be a proportion of the sum of everything
that you allow to be included:
sums, palynological richness, aquatics, etc. If accumulation
rates are being calculated by the program, this is done before producing the
reduced dataset for any analysis. Accordingly, the threshold set should be
appropriate for the calculated accumulation rates, not the input
concentrations values.
Return to main menu.
Back to contents page
Copyright © 1995-2007 K.D. Bennett
Archaeology and Palaeoecology | 42 Fitzwilliam St | Belfast BT9 6AX | Northern Ireland | tel +44 28 90 97 5136
Archaeology and Palaeoecology | The 14Chrono Centre | URL http://www.qub.ac.uk/arcpal/ |
WebMaster