Chapter 15 Kruskal-Wallis.....Psyc205/Soc205.....Vernoy

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Chapter 15
Kruskal-Wallis Test

I. Assumptions

A. One independent variable

B. Three or more independent groups

C. Rank data

II. Rank the Data

A. Combine the groups and rank the data

B. Lowest score gets a rank of 1

C. Tied scores get the same rank

(Average the ranks the scores would normally get)

III. Separate the ranks into their original groups

A. Sum the ranks for sample 1 ()

B. Sum the ranks for sample 2 ()

C. Sum the ranks for sample 3 ()

D. Continue for all k samples

IV. Compute H (The Kruskal-Wallis test statistic)

V. The significance of H

A. Degrees of freedom = k-1

B. Find the critical value in Table X (The Chi Square Distribution)

C. If H is > or = the critical value then reject H_o

D. If H is < the critical value then fail to reject H_o