# AFNI program: p2t

## Output of -help

*** NOTE: This program has been superseded by program 'cdf' ***
Usage #1: p2t p dof
where p = double sided tail probability for t-distribution
dof = number of degrees of freedom to use
OUTPUT = t value that matches the input p
Usage #2: p2t p N L M
where p = double sided tail probability of beta distribution
N = number of measured data points
L = number of nuisance parameters (orts)
M = number of fit parameters
OUTPUT = threshold for correlation coefficient
Usage #3: p2t p
where p = one sided tail probability of Gaussian distribution
OUTPUT = z value for which P(x>z) = p
Usage #4: p2t p dof N
where p = double sided tail probability for distribution of
the mean of N iid zero-mean t-variables
dof = number of degrees of freedom of each t-variable
N = number of t variables averaged
OUTPUT = threshold for the t average statistic
N.B.: The method used for this calculation is the Cornish-
Fisher expansion in N, and is only an approximation.
This also requires dof > 6, and the results will be
less accurate as dof approaches 6 from above!

**This page auto-generated on
Wed Jul 26 08:47:10 EDT 2006
**