Experimental Group Control Group

Time (min) Rank Time (min) Rank

140 4 130 1

147 6 135 2

153 8 138 3

160 10 144 5

165 11 148 7

170 13 155 9

171 14 168 12

193 15

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(N₁=8; R₁=81) (N₂=7; R₂=39)

N= Number of participants in each group

R= the total when we add all of the ranks together

STEP 3: Now use the following formula to find U (U= Hypothetical Data).

R=Rank; N=Total Number of Observations

U=N₁*N₂+ N₁(N₁+1)-R₁

Example: U = (8) x (7) + 8*(9) - 81

U= 56 + (8 x 9) - 81

U = 56 + 72 – 81

U= 128 – 81 = 47

U = 47

STEP 4: Go to the Mann-Whitney Chart/Table (on the next page).

· U = 47.

· Is 47 between the N₁ to N₂ range of numbers on the chart?

· If YES, then reject the NULL Hypothesis.

· If NO, then accept the NULL Hypothesis.

· 47 is NOT between the N₁ to N₂ range of numbers on the chart so we must accept the Null hypothesis.

· This means that our independent variable (IV) did not make a significant difference in the results (Dependent Variable, DV).

Wilcoxon Signed-Ranks Test

· This test is used for the repeated measures design to see if there is a significant difference between the before and after trials of your experiment.

· The significance for this test must also be 0.05 (called the Alpha Level for this test).

· This test involves finding the “critical Z-score” from a Z-table which is 1.96.

· If your Z-score is less than -1.96 or greater than 1.96 then reject the null and accept your alternate hypothesis (H₁).

· This will mean that your Independent Variable (IV) did make a significant difference.

Step 1: Make a chart showing the scores before and after.

Before After

28 12

17 31

36 19

35 14

32 20

33 19

Step 2: Add a 3^rd column showing the difference between the before and after scores. You find this difference by subtracting.

Date: 2015-01-11; view: 1296