Chapter 15 Wilcoxen.....Psyc205/Soc205.....Vernoy

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Chapter 15
Wilcoxen T

I. Assumptions

A. Nonparametric data

B. One independent variable

C. Two correlated samples

II. Procedure for finding the Wilcoxen T

A. Compute the differences between the pairs of scores

B. Exclude all zero differences from the rest of the procedure

C. Rank the differences according to absolute value (+2 gets the same rank as -2)

D. The smallest score, according to absolute value, gets a rank of one

E. Tied ranks get the average of the ranks

F. Sign the ranks

1. If the difference score was negative the rank is assigned to the minus category

2. If the difference score was positive the rank is assigned to the plus category

G. Sum the ranks

1. Sum the plus ranks ()

2. Sum the minus ranks ()

(Remember: and are always positive numbers)

H. The Wilcoxen T is the smaller of the and

III. The significance of T...Using Table W

A. Count up the number of signed ranks

(Number of pairs) - (Number of zero differences)

B. Using the number of signed ranks find the critical value in Table W

C. If T = or < the critical value from Table W then reject H_o

D. If T > the critical value from Table W then fail to reject H_o