Dear All,

I have a issue about two-tailed inverse of the student`s t-distribution. I am trying to use calculation for two-tailed inverse of the student`s t-distribution function presented by Excel functions like =TINV(probability, deg_freedom).

alpha (a)= 0.05
degree of freedom (df)= 1221
p (two-tailed)= 0.0000408831

Next, just do calculate for two-tailed INVERSE of the student`s t-distribution using Excel formula as below;

=TINV(probability, deg_freedom)
=TINV(0.0000408831, 1221)
= 4.117456798

Resulted: 4.117456798

Could you show me a manual calculation step by step for TINV function.

Appreciate your helps in advance. Thanks