t-Values

Note: The 95% column has been highlighted, since that is only Confidence Level you will be required to cite in the Level 4 Lab courses.

Degrees of Freedom (n-1)	Confidence Level
	90%	95%	99%	99.9%
1	6.314	12.706	63.657	636.619
2	2.920	4.303	9.925	31.598
3	2.353	3.182	5.841	12.941
4	2.132	2.776	4.604	8.610
5	2.015	2.571	4.032	6.859
6	1.943	2.447	3.707	5.959
7	1.895	2.365	3.499	5.405
8	1.860	2.306	3.355	5.041
9	1.833	2.262	3.250	4.781
10	1.812	2.228	3.169	4.587
11	1.796	2.201	3.106	4.437
12	1.782	2.179	3.055	4.318
13	1.771	2.160	3.012	4.221
14	1.761	2.145	2.977	4.140
15	1.753	2.131	2.947	4.073
16	1.746	2.120	2.921	4.015
17	1.740	2.110	2.898	3.965
18	1.734	2.101	2.878	3.922
19	1.729	2.093	2.861	3.883
20	1.725	2.086	2.845	3.850
21	1.721	2.080	2.831	3.819
22	1.717	2.074	2.819	3.792
23	1.714	2.069	2.807	3.767
24	1.711	2.064	2.797	3.745
25	1.708	2.060	2.787	3.725
26	1.706	2.056	2.779	3.707
27	1.703	2.052	2.771	3.690
28	1.701	2.048	2.763	3.674
29	1.699	2.043	2.756	3.659
30	1.697	2.042	2.750	3.646
40	1.684	2.021	2.704	3.551
50	1.676	2.009	2.678	3.496
60	1.671	2.000	2.660	3.460
80	1.664	1.990	2.639	3.416
100	1.660	1.984	2.626	3.390
120	1.658	1.980	2.617	3.371
1000	1.646	1.962	2.581	3.300
Infinite	1.645	1.960	2.576	3.291
Degrees of Freedom (n-1)	90%	95%	99%	99.9%
	Confidence Level

EXAMPLE: Assume we have a set of five readings with an average value of 23.471 and a Standard Error of 0.799.

Since there are five readings (n = 5) there are (n - 1) = 4 Degrees of Freedom.

Looking at the table, we read across from the Degrees of Freedom = 4 row and down the 95% column to find a t_95% of 2.776.

Therefore the 95% confidence level for the value is SE*t_95% = 0.799*2.776 = 2.218 (Value = 23.5 ± 2.2).

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