Factors Affecting Choice Of Statistical Tests Including Levels Of Measurement And Design

Question 1

Descriptive Statistics

Answer 1

Descriptive statistics can give summaries of data that we have collected from our research; and an indication of what the statistical analysis might reveal about our results. Levels of Measurement are used to try to categorise our data into one of four types, so that we can correctly select the most appropriate statistical test to analyse our results

Question 2

Different levels of measurement

Answer 2

Nominal
Ordinal
Interval

Question 3

Nominal

Answer 3

The data consists of the numbers of participants that might fall into different categories, and a person can be placed in one category only and not the other

Question 4

Ordinal

Answer 4

The data can be placed in rank order from lowest to highest. The ordinal scale can consist of measurements that are of unequal intervals e.g. 1.20, 1.25, 1.27. The data is concerned with the order that the data can be presented in.

Question 5

Interval

Answer 5

The data has fixed and even intervals (and this differs from ordinal data). The units of data are fixed (and have the same distance) throughout the range.

Question 6

Different types of statistical tests

Answer 6

Chi Squared
Spearman’s Rho
Mann Whitney
Wilcoxon
Pearson r
Related T test
Unrelated T test

Question 7

Parametric tests Vs non-parametric tests

Answer 7

Parametric tests are more robust and powerful than non-parametric tests. They rely on the actual data collected rather than just examining the rank order of the data. Parametric tests are also more likely to detect if the data is significant or not. There are three factors that mean a parametric test can be conducted:

a) Interval level of measurement:
The data must be interval rather than ordinal in terms of level of measurement
b) Normal distribution:
The data collected should be taken from a population that shows a normal distribution curve rather than a skewed distribution
c) Variance of data:
The data should have similar variance or spread of scores. This can be examined by looking at the dispersion of the data and the standard deviations for both conditions and seeing if they are similar

Question 8

How do you decide what test to use

Answer 8

1) Does the research involve a correlation, a test of difference, or an association?

• If using a correlation then you should use Spearman’s Rho or Pearson’s r
• If looking for a test of difference, then you should use one of these tests Mann Whitney, Chi Squared, Wilcoxon, Unrelated t-test, or Related t-test
• If looking for an association between variables then you would use Chi squared

2) Which research design is being used?

• Independent measures
• Repeated measures or
• Matched participants design

3) Which level of measurement is being used in the research?

• Decide between nominal, ordinal and interval

Question 9

Non parametric tests

Answer 9

Chi squared
Sign test
Chi squared (association)
Mann Whitney U test
Wilcoxon
Spearman’s rho (correlation)

Question 10

Parametric tests

Answer 10

Unrelated T test
Related T test
Pearson’s r (correlation)

Question 11

Nominal data test

Answer 11

Chi squared
Sign test
Chi squared (association)

Question 12

Ordinal data test

Answer 12

Mann Whitney U test
Wilcoxon
Spearman’s rho (correlation)

Question 13

Interval data test

Answer 13

Unrelated T test
Related T test
Pearsons r (correlation)

Question 14

Independent measures test

Answer 14

Chi squared
Mann Whitney U test
Unrelated T test

Question 15

Repeated measures/matched participants design tests

Answer 15

Sign test
Wilcoxon
Related T test

Question 16

Test of association or correlation

Answer 16

Chi squared (association)
Spearman rho (correlation)
Pearson’s r (correlation)