Table entry for C is the critical value *required for confidence level C To approximate one- and two-sided P-values, compare the value of the t that match the P-values given at the bottom of the table. TABLE C t distribution critical values Confidence level C freedom 50% 96% 99% 99.8% 99.9% 1.000 1.963 6.314 15.89 31.82 63.66 318.3 636.6 0.816 1.061 4.303 4.849 9.925 14.09 22.33 31.60 0.765 0.978 1.250 2.353 3.182 3.482 7.453 0.741 0.941 1.533 2.132 2.776 2.999 4.604 5.598 2.015 7.173 8.610 0.727 2.757 3.365 4.032 4.773 0.718 1.943 2.447 3.143 3.707 1.895 2.365 2.998 4.785 0.706 0.889 1.860 2.449 3.355 3.833 0.703 1.833 2.398 2.821 3.250 0.700 0.879 1.812 2.764 4.587 11 0.697 0.876 1.088 1.363 1.796 2.328 3.497 12 0.695 0.873 1.083 2.681 3.428 3.930 13 0.694 0.870 2.282 14 3.012 3.852 0.692 1.076 1.345 2.145 3.787 0.866 1.074 1.753 2.249 2.602 2.947 3.286 3.733 0.690 2.120 2.235 2.583 2.921 3.252 17 0.689 0.863 1.333 2.110 2.224 2.567 3.222 3.646 3.965 18 0.688 0.862 1.067 1.330 2.101 2.214 3.197 3.922 19 0.861 1.729 2.205 2.539 3.579 1.064 1.325 2.086 3.153 3.552 21 1.323 1.721 2.080 2.831 3.135 3.527 3.819 22 0.686 1.717 2.074 2.183 2.508 2.819 3.119 3.505 0.685 0.858 1.714 2.069 2.500 2.807 24 0.685 0.857 1.059 2.172 25 1.711 2.492 2.797 3.091 3.745 0.684 1.708 2.060 2.167 2.485 2.787 3.725 0.684 1.058 1.706 2.162 0.855 1.703 2.052 2.158 28 0.683 2.473 2.771 3.057 3.690 1.701 29 2.154 2.467 2.763 3.047 3.408 3.674 1.055 2.045 30 0.683 2.150 2.462 2.756 3.038 0.854 1.055 1.310 1.697 2.147 3.030 40 0.681 0.851 1.050 1.684 2.123 2.423 2.704 2.971 50 0.679 0.849 1.299 1.676 2.009 2.109 2.403 0.848 2.937 1.296 2.000 2.660 2.915 80 3.232 3.460 0.678 0.846 1.292 1.664 1.990 2.088 2.374 2.887 100 1.290 1.660 1.984 2.081 2.364 2.626 0.842 1.282 2.056 2.330 2.813 3.098 0.674 0.841 1.282 2.054 2.326 2.576 2.807 One-sided P .25 .20 15 .10 .05 025 02 .01 005 0025 001 Two-sided P .30 .20 .05 .01 005 002 001