Factors affecting choice of Stat test

Question 1

8 stat tests

Answer 1

• Sign test
• Chi-Squared test
• Wilcoxon
• Mann-Whitney
• Related t-test
• Unrelated t-test
• Spearman’s rho
• Pearson’s r

Question 2

choose the appropriate statistical test, there are three questions that need to be answered

Answer 2

1. Do we need a test of difference or a test of relationship?
2. If test of difference – what type of experimental design has been used?
   If test of relationship – are we looking for an association or correlation?
3. What level of data has been collected?

Question 3

appropriate statistical test can be identified from the table below

Answer 3

Test of Difference:
Independent groups:………..Repeated Measures:

Nom: Chi-squared Test…….Sign Test
Ord: Mann-Whitney U……….Wilcoxon
Int: Unrelated t-test…………..Related t-test

Test of Relationship
Association:……………..Correlation:
Nom: Chi-squared ……………. -
Ord: - ………………….Spearmans rho
Int: - ………………….. Pearsons’s are

Question 4

non-parametric tests

Answer 4

*Spearman’s rho
*Wilcoxon
*Mann-Whitney
*Chi-Squared test
*Sign test

Question 5

parametric tests

Answer 5

*Pearson’s r
*Related t-test
*Unrelated t-test

Question 6

Why are parametric tests are preferred to non-parametric tests

Answer 6

Parametric tests are preferred to non-parametric tests as they are more powerful. This means that they are more likely to detect significance. However, there are 3 conditions that must be met in order for them to be used:

1. Data must be interval level.
2. Population data must be normally distributed (remember that many characteristics are normally distributed such as height, weight, IQ etc).
3. The variances (based on standard deviation) for the two sets of data should be similar. This is termed ‘homogeneity of variance’.