Finding critical value $t^*$ given a confidence level of $C$%, using the table with critical $t$ values

Assuming a table with a row per degrees of freedom and a column per upper tail probability

  1. Find the row with the appropriate degrees of freedom (df)
  2. Find the column for the upper tail probability equal to $\frac{1\,-\,C/100}{2}$
  3. At the intersection point of this row and column, you find the critical value $t^*$
Critical t value given confidence level C