In a portion of a study of self-awareness, Dana (1990) observed the values
59, 106, 174, 207, 219, 237, 313, 365, 458, 497, 515, 529, 557, 615, 625, 645, 973, 1065, 3215
Compare the lengths of the confidence intervals based on the mean and 20% trimmed mean. Why is the latter confidence interval shorter?