In statistics, the folded-t and half-t distributions are derived from Student's t-distribution by taking the absolute values of variates.
This is analogous to the folded-normal and the half-normal statistical distributions being derived from the normal distribution.
degrees of freedom; its probability density function is given by:[citation needed] The half-t distribution results as the special case of
, and the standardized version as the special case of
Its probability density function then simplifies to The half-t distribution's first two moments (expectation and variance) are given by:[1] and Folded-t and half-t generalize the folded normal and half-normal distributions by allowing for finite degrees-of-freedom (the normal analogues constitute the limiting cases of infinite degrees-of-freedom).