Kruskal-Wallis Test Access tech supplements, videos, and data sets at www.TriolaStats.com TECH CENTER continued R R command: kruskal.test(list(x, y, z)) A complete list of R statistical commands is available at TriolaStats.com Excel XLSTAT Add-In (Required) 1. Click the XLSTAT tab in the Ribbon and click Nonparametric tests. 2. Select Comparison of k samples from the dropdown menu. 3. In the Samples box enter the data range for the sample values. If the range includes labels, check the Column labels box. 4. Select One column per sample under Data format. 5. Check the Kruskal-Wallis test option only. 6. Click the Options tab, enter a significance level and check the Asymptotic p-value box. 7. Click the Missing Data tab and select Ignore missing data if the data samples do not have an equal number of observations. 8. Click OK. 13-5 Kruskal-Wallis Test for Three or More Samples 675 Statistical Literacy and Critical Thinking 1.HIC Measurements Listed below are head injury criterion (HIC) measurements from crash tests of small, midsize, large, and SUV vehicles. In using the Kruskal-Wallis test, we must rank all of the data combined, and then we must find the sum of the ranks for each sample. Find the sum of the ranks for each of the four samples. Small 29 31 35 33 26 32 21 Midsize 32 28 26 23 25 Large 27 32 39 27 31 26 SUV 24 31 31 25 30 39 22 2. Requirements Assume that we want to use the data from Exercise 1 with the Kruskal-Wallis test. Are the requirements satisfied? Explain. 3. Notation For the data given in Exercise 1, identify the values of n1, n2, n3, and N. 4. Efficiency Refer to Table 13-2 on page 645 and identify the efficiency of the Kruskal-Wallis test. What does that value tell us about the test? Using the Kruskal-Wallis Test. In Exercises 5–8, use the Kruskal-Wallis test. 5.HIC Measurements Use the sample data from Exercise 1 with a 0.05 significance level to test the claim that small, midsize, large, and SUV vehicles have the same median HIC measurement in car crash tests. 6.Arsenic in Rice Listed below are amounts of arsenic in samples of brown rice from three different states. The amounts are in micrograms of arsenic and all samples have the same serving size. The data are from the Food and Drug Administration. Use a 0.01 significance level to test the claim that the three samples are from populations with the same median. Arkansas 4.8 4.9 5.0 5.4 5.4 5.4 5.6 5.6 5.6 5.9 6.0 6.1 California 1.5 3.7 4.0 4.5 4.9 5.1 5.3 5.4 5.4 5.5 5.6 5.6 Texas 5.6 5.8 6.6 6.9 6.9 6.9 7.1 7.3 7.5 7.6 7.7 7.7 13-5 Basic Skills and Concepts
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