Find the critical value, tc, for c = 0.90 and n = 13. *Please show all the steps* Solution assuming this is a one tailed critical value, you know =.10 and the degrees of freedom are 13- 1=12. So go to the t distribution table [t-table] and find the row with d.f. = 12 and look for the coloumn labeled \"t.10\" you should find that the critical value is 1.356.