a) Calculate the 10% trimmed mean for the data on test performance in Figure 4.1. (Remember that 10% trimming means removing the 10% of the scores at each end of the distribution.)

b) Assume that you collected the following data on the number of errors that participants made in reading a passage under distracting conditions.

10 10 10 15 15 20 20 20 20 25 25 26 27 30 32 37 39 42 68 77 Calculate the 10% trimmed mean for these data.

c) Trimming made more of a difference in (b) than it did in (a). Can you explain why this might be?

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Figure 4.1 Score on items when passage not read Raw Data: 54 52 51 50 36 55 44 46 57 44 43 52 38 46 55 34 44 39 43 36 55 57 36 46 49 46 49 47 Descriptives Score for Mean Statistic Std. Error 46.5714 1.29041 nonpassage group 95% Confidence Interval for Mean Lower Bound 43.9237 Upper Bound 49.2191 5% Trimmed Mean 46.6587 Median 46.0000 Variance 46.624 Std. Deviation 6.82820 Minimum 34.00 Maximum 57.00 Range 23.00 Interquartile Range 9.0000 Skewness -.224 .441 Kurtosis -.901 .858