Silk Purse Spreadsheet R. H. Zander Res Botanical Web Site March 24, 2005 
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
various papers submitted for publication, see my reprint URLs. For more information,
contact author To download the
spreadsheet, click here. 
