A veterinarian collects data on the number of times race horses are raced during their careers. The veterinarian finds that the average number of races a horse enters is ¯ x = 15.3 , with a standard deviation of s = 6.8 in a sample of n = 20 horses. For a 95% confidence interval, the veterinarian should choose the critical value to be: 2.093. 1.729. 1.96. 1.645.