Stats Tests

Question 1

Stats Tests-
Spearman’s Rho

Criteria

Answer 1

Spearman’s Rho
Criteria:
-Hypothesis states a CORRELATION between 2 CO VARIABLES
-The sets of data are INTERVAL- pairs of scores from ONE PERSON’
-The data is ORDINAL

Question 2

Stats Tests-
Spearman’s Rho

Formula

Answer 2

Rs- 6 E D2
1- —————
n(n2-1)
D= Difference
n= Number
Rs= Spearman’s Rho

1) Rank the data
2) Calculate the difference, Square difference and add up total to get D2
3) Calculate observed value of Rs

Question 3

Stats Tests-
Chi Square

Criteria

Answer 3

Chi Square
Criteria:
-Hypothesis tests DISTRIBUTION OF OBSERVATIONS in to categories- DIFFERENCES in data, relationship between 2 variables
-Uses INDEPENDENT GROUPS DESIGN, divisions within categories must be EXCLUSIVE- person full into one and only ONE of these categories
-Looks at PATTERN of OBSERVATIONS, will tell us if certain combinations of categories occur more frequently that we would EXPECT by change
-Data is NOMINAL
-Uses CONTINGENCY TABLE

Question 4

Stats Test-
Chi Square

Formula

Answer 4

X2= (o-e)2
E ————-
e
O= Observed value
e= Expected value
X2= Chi square value

1)Put raw data into contingency table
2) For each cell in original contingency table calculate EXPECTED VALUE= row total x column total
————————————
Grand total
3) For each cell SUBTRACT the expected value from the OBSERVED VALUE= (o-e)
4)SQUARE the values from the previous step= (o-e)2
5)DIVIDE the results from the previous step by e
6)Add up all the values to get X2
7)To find out if value is SIGNIFICANT- work out DEGREES OF FREEDOM= (rows-1)x(column-1)

Question 5

Stats Tests-
Mann Whitney U

Criteria

Answer 5

Mann Whitney U
Criteria:
-The hypothesis states a DIFFERENCES between the 2 sets of data
-The sets of data are INDEPENDENT DATA from separate groups
-The data is ORDINAL

Question 6

Stats Tests-
Mann Whitney U

Formula

Answer 6

Ua= nQnB + na (na +1)
—————— - ERa
2
Na=
Nb=

Ub= nAnB + nb(nb+1)
-—————- - ERb
2. Ra=
Rb=

Question 7

Stats Tests-
Wilcoxon T

Criteria

Answer 7

Wilcoxon T
Criteria:
-The hypothesis states a DIFFERENCE between the 2 sets of data
-The sets of data are REPEATED PAIRS of scores from one person
-The data is ORDINAL

Question 8

Stats Test-
Wilcoxon T

Formula

Answer 8

1) Find the DIFFERENCE
2) RANK the difference
3) Rank POSITIVE and NEGATIVE rank values
4) ADD UP the positive and negative values
5) SMALLEST NUMBER= T value
6) N value= no of NON ZERO DIFFERENCES
7) Find CRITICAL VALUE

Question 9

Levels of significance

Answer 9

• The significance level= the probability of rejecting the NULL HYPOTHESIS when it is TRUE
• eg significance level: 0.05 indicates 5% risk of concluding a difference exists when there is no ACTUAL DIFFERENCE
• Mainly use 0.05
• 0.01 only used in situations where the research is testing an important medical treatment

Question 10

Drawing Conclusions

Answer 10

• Always state the result from the statistical test, the comparison between the critical and calculated value
• State whether the result is SIGNIFICANT or NOT
• Refer back to your HYPOTHESES stating which one you will ACCEPT, and which one you will REJECT
• Explain how the FINDINGS relate to your ORIGINAL PROBLEM and if the results SUPPORT, or CONTRADICT any previous research mentioned