Miner, Please explain how to refer these tables for following values:
T-static=.1224
df=14
alpha=0.05
Thanks in advance
First decide whether it is a one or two-tailed test.
I will illustrate using the University of Missouri's table and a two-tailed test.
Use the Tail Probability, 2-tailed column on the left side and follow it down to the row marked 0.05. This is the alpha value. Follow this row across to the right until it intersects the two columns marked 12 and 15 degrees of freedom.
The critical value of t for 12 df is 2.179 and for 15 df is 2.131. You can interpolate the critical t-value for 14 as follows.
(15-14)/(15-12) = (t - 2.131)/(2.179 - 2.131)
1/3 = (t-2.131)/0.048
0.048/3 = t - 2.131
0.016 + 2.131 = t
t = 2.147; If the t - statistic is >= 2.147, then Ho is rejected.
In your case t = 0.1224. This is << the critical value of t (2.147), so you fail to reject Ho.
Ho: there is no difference (because this is a 2 - tailed test)
Ha: there is a difference