Use a t-table, software, or a calculator to estimate the following critical values. a) The critical value of t for a 99% confidence interval with df = 21. b) The critical value of t for a 98% confidence interval with df = 88. Click the icon to view a t-distribution table of critical values. . . . a) What is the critical value of t for a 99% confidence interval with df = 21? (Round to two decimal places as needed.)t-table 12/1 1/22, 12:43 AM 0.20 0.10 0.05 0.02 0.01 Two-tail probability 0.10 0.05 0.025 0.01 0.005 One-tail probability Table T df 31.821 Values of to 3.078 6.314 12.706 63.657 9.925 1.886 2.920 4.30 6.96 1.639 2.353 3.182 4.541 5.841 2.776 3.747 4.604 1.533 2.132 1.47 2.01 2.57 3.365 4.032 1.440 1.943 2.44 3.143 3.707 1.895 2.365 2.998 3.499 1.415 1.397 1.860 2.306 2.896 3.355 1.383 1.833 2.262 2.821 Two tails 2.764 3.169 10 10 1.372 1.812 2.228 2.201 2.718 3.106 11 11 1.363 1.796 12 1.356 1.782 2.179 2.681 3.055 12 13 13 1.350 1.77 2.160 2.650 3.012 2.977 14 14 1.345 1.761 2.145 2.624 15 1.34 1.753 2.131 2.602 2.947 15 2.921 One tail 16 1.337 1.746 2.120 2.583 16 17 1.33 1.740 2.110 2.567 2.898 17 18 1.330 2.552 18 1.734 2.101 2.878 19 19 1.729 2.093 2.539 2.861 1.328 1.325 1.725 2.086 2.528 2.845 20 1.721 2.518 2.831 1.32 2.080 21 1.321 1.717 2.07 2.508 2.819 22 2.500 2.807 23 1.319 1.714 2.069 1.318 1.711 2.064 2.492 2.797 24 1.316 1.708 2.060 2.48 2.787 2.056 2.779 1.315 1.706 2.479 1.314 1.703 2.05 2.473 2.771 1.313 1.701 2.045 2.46 2.763 1.311 1.699 2.045 2.462 2.756 1.697 2.45 30 1.310 2.04 2.750 1.30 1.694 2.037 2.44 2.738 32 1.306 2.030 2.438 2.725 35 1.690 40 1.303 1.684 2.021 2.423 2.704 1.301 1.679 2.690 45 2.014 2.412 45 2.009 2.403 2.678 50 50 1.295 1.676 60 1.671 2.000 2.390 2.660 1.296 75 1.293 1.665 1.992 2.377 2.643 1.290 1.660 1.98 2.364 2.626 100 100 120 1.289 1.658 1.980 2.358 2.617 120 140 1.288 1.656 1.97 2.353 2.61 140 180 1.653 2.347 2.60 180 1.286 1.97 1.651 1.969 2.341 2.596 250 250 1.285 400 1.284 1.649 1.96 2.336 2.58 400 1000 1.282 1.96 2.330 1000 1.646 2.581 1.645 1.960 2.326 2.576 1.282 90% 95% 98% 99% Confidence levels 80%