Chapter 12 . Testing Relationships 115 TABLE 12-3 Finding Statistical Significance Using the t-Distribution Number of Tails in Test Confidence Level Degrees of Freedom t-Observed Two 99% t-Critical Statistically Significant 21 2.95 2.831 yes Two 95% 25 -3.10 Two 95% 15 -2.12 Two 90% 10 1.94 Two 90% 18 1.57 One 99% 12 -2.46 One 99% 23 2.38 98.5% 40 -2.30 One 95% 28 1.89 One 1.68 95% 16 One