Critical t-value calculator - 2017

This is a refactored version of Joris Meurs' critical t function.

This function is a refactored version of submission 54369 "critical-t-value-calculator" by Joris Meurs.
% critt looks up the critical t-value for specific cases.
%
% Used for getting the t-statistic for a number of degrees of freedom (1 to 100),
% a particular level of confidence (90%, 95%, or 99%), and either one or
% two tailed values.
%
% Usage:
% tValue = CritT(alfa,v,tail)
%
% Where:
% alfa is the significance level, specified as a fractional value.
% Supported values are 0.10 (90% confidence), 0.05 (95%), and 0.01 (99%).
% v is the number of degrees of freedom. Supported values are integers from 1 to 100.
% tail is the selector between a one- and two-tailed t-value. Supported
% values are 'one', and 'two'.
% tValue is the criticalt-value output.
%
% Table with alfa values and corresponding t-values were obtained by using
% the icdf functions.
%
% Developed by Joris Meurs BASc (2015)
%
% Edited by Francis Esmonde-White (2017)