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t-table
Student's t test

Note 1: A difference between two means is significant (at the given probability level) if the calculated t value is greater than the value given in this table. A probability of p = 0.05 (95% probability of making a correct statement) is usually acceptable for biological work, but p = 0.1 can be used for a "one-tailed" t-test.

Note 2: When comparing two means, the number of degrees of freedom is (n1 + n2)-2, where n1 is the number of replicates of treatment 1, and n2 is the number of replicates of treatment 2.

Note 3: This table does not show all degrees of freedom. If you want a value between, say 30 and 40, then use the value for 30 df.

Degrees of Freedom

Probability, p

  0.1 0.05 0.01 0.001
1 6.31 12.71 63.66 636.62
2 2.92 4.30 9.93 31.60
3 2.35 3.18 5.84 12.92
4 2.13 2.78 4.60 8.61
5 2.02 2.57 4.03 6.87
6 1.94 2.45 3.71 5.96
7 1.89 2.37 3.50 5.41
8 1.86 2.31 3.36 5.04
9 1.83 2.26 3.25 4.78
10 1.81 2.23 3.17 4.59
11 1.80 2.20 3.11 4.44
12 1.78 2.18 3.06 4.32
13 1.77 2.16 3.01 4.22
14 1.76 2.14 2.98 4.14
15 1.75 2.13 2.95 4.07
16 1.75 2.12 2.92 4.02
17 1.74 2.11 2.90 3.97
18 1.73 2.10 2.88 3.92
19 1.73 2.09 2.86 3.88
20 1.72 2.09 2.85 3.85
21 1.72 2.08 2.83 3.82
22 1.72 2.07 2.82 3.79
23 1.71 2.07 2.82 3.77
24 1.71 2.06 2.80 3.75
25 1.71 2.06 2.79 3.73
26 1.71 2.06 2.78 3.71
27 1.70 2.05 2.77 3.69
28 1.70 2.05 2.76 3.67
29 1.70 2.05 2.76 3.66
30 1.70 2.04 2.75 3.65
40 1.68 2.02 2.70 3.55
60 1.67 2.00 2.66 3.46
120 1.66 1.98 2.62 3.37
1.65 1.96 2.58 3.29

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