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Silk Purse Spreadsheet R. H. Zander Res Botanical Web Site Missouri Botanical Garden March 24, 2005 |
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This MS Excel spreadsheet allows
calculation of confidence intervals for each composite internode created from
several internodes on a cladogram with less than fully reliable confidence
intervals. The chance of at least one
of two or more chained internodes being correct is calculable with a simple
probability formula, namely one minus (the product of the chances each
internode is incorrect), where the chance of being incorrect is 1 minus the
CL (or BPP). This is the Formula for Implied Reliability. In addition, a spreadsheet
calculation for Bayes’ Formula is given. One may produce a posterior
probability for a branch arrangement by using as a prior a previous result
for that branch arrangement. For morphological results, assign an arbitrary
0.95 prior if the branch arrangement agrees with molecular result, 0.05 if
disagrees, 0.50 if equivocal or contested. Note that previously published branch
arrangements less than 0.50 probability must be included to avoid simply
choosing probabilities greater than 0.50, which will always increase the
posterior probability. This spreadsheet supports papers
submitted for publication: "A taxonomists' guide to interpreting
cladograms, with the problematic taxa Timmiella,
Hypodontium and Rhabdoweisiaceae (Bryophyta) as examples,” “The
Pottiaceae s.str. as an evolutionary Lazarus taxon. J. Hattori Bot. Lab. 2006,”
and “Multiple test problems with
cladograms and six mitigations.” For more information,
contact author Richard Zander richard.zander@mobot.org
To download the
spreadsheet, click here. |
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