Y13 RESEARCH METHODS - NON PARAMETRIC: mann-whitney and wilcoxon

Question 1

when do you use mann whitney?

Answer 1

1. looking for a difference between groups
2. independant groups design
3. ordinal data

Question 2

STEP 1 of Mann Whitney?

Answer 2

TABLE of RANKS
- look at data from both groups and start by giving the lowest number a rank of 1 and work upwards.
- calculate the sum of ranks

Question 3

STEP 2 of Mann Whitney?

Answer 3

Working out the value of U

• calculate the smaller value of U
• Na = number of Ps in group
• Ua = smallest sum

U= Ua = Ra - [Na (Na + 1)]/2
U = calculated value

Question 4

mann whitney step 3? Calculated value vs critical value?

Answer 4

critical value > calculated value
= significant difference

Question 5

when to use Wilcoxon?

Answer 5

1. looking for a difference ( between 2 groups/ sets of data)
2. repeated measures design ( related = same ppl in both groups)
3. ordinal data ( individual scores that can be put in order)

Question 6

step 1 of Wilcoxon?

Answer 6

• calculate the difference between the sets of data including a + or - sign
• data with no difference are not included in the ranking
• rank the difference

Question 7

step 2 of wilcoxon?

Answer 7

working out the value T :
- the calculated value of T is the sum of the less frequent sign
( whether there is more + values or - values)

Question 8

step 3 of wilcoxon?

Answer 8

critical value > calculated value of T
for significance to be shown