TINV function

 Returns the inverse of the Student's t-distribution


 * TINV(probability,deg_freedom)
 * Probability - the probability associated with the two-tailed Student's t-distribution.
 * Deg_freedom - the number of degrees of freedom with which to characterize the distribution.
 * If either argument is nonnumeric, TINV returns the #VALUE! error value.
 * If probability <= 0 or if probability > 1, TINV returns the #NUM! error value.
 * If deg_freedom is not an integer, it is truncated.
 * If deg_freedom < 1, TINV returns the #NUM! error value.
 * TINV returns that value t, such that P(|X| > t) = probability where X is a random variable that follows the t-distribution and P(|X| > t) = P(X < -t or X > t).
 * A one-tailed t-value can be returned by replacing probability with 2*probability. For a probability of 0.05 and degrees of freedom of 10, the two-tailed value is calculated with TINV(0.05,10), which returns 2.28139. The one-tailed value for the same probability and degrees of freedom can be calculated with TINV(2*0.05,10), which returns 1.812462.
 * Given a value for probability, TINV seeks that value x such that TDIST(x, deg_freedom, 2) = probability. Thus, precision of TINV depends on precision of TDIST. TINV uses an iterative search technique. If the search has not converged after 100 iterations, the function returns the #N/A error value.