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Jul 4, 2014

Simple Probit Analysis

A dialogue lets the user assign variables as doses, counts of successes and

totals. If desired; a logarithmic transformation may be applied to the dose

variable. The script calculates and adds all columns neeeded to perform a

nonlinear regression for the parameters of a probit regression for dose. The

user dialogue asks for #Responses, #Total and Dose. The script adds columns for

relative frequency of the "successes", the probit function and the loss

function. After estimating the regression parameters the report with a set of

inverse predictions and a graph of the fit is displayed. The prediction column

is appended to the data table.

Application: Dose response tests are routine in

lab experiments to assess efficcacy or toxicity of agents. The results are

reported as totals and counts of events. The probit regression estimates the

probability to observe an event as a function of the dose applied. Knowing the

regression function alows for the calculation of frequently used indicators like

ED50, ED90 or so on. A set of these estimators along with their confdence

intervals is part of the report.

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