On your white boards… Write an example of Nominal data… Write an example of Ordinal data… Write an example of Interval/ratio data…

On your white boards…

Write an example of Nominal data…Write an example of Ordinal data…Write an example of Interval/ratio data…

Types of Data: This dictates which test you use… Nominal Data: Used for exclusive groups or categories e.g. Male or female, Psychology graduate or Sociology Graduate.

Then frequencies are recorded for each group.

Ordinal Data: Order of things e.g. Medallists at the Olympics, Horses in a race We do not measure the gaps/intervals, (BUT note: they maybe different sizes)

Interval or Ratio Data: Measure on a scale e.g. temperature, distance The gaps/intervals are equal

Which statistical test do we use to find our observed value? Decision 1: What are you looking for?

Differences Correlation

Decision 2: What level of measurement? Spearman’s rho

Nominal Ordinal and Interval/Ratio

Chi squared test

Decision 3: What experimental design

Independent groups

Repeated measures/ or

matched

Mann Whitney U test

Wilcoxon matched

pairs rank test

If I am… Measuring a difference and have nominal data I would use…

Chi Squared

If I am… Measuring a difference and have interval/ratio data and I have independent groups I would use…

Mann-Whitney U

If I am… Measuring a difference and have interval/ratio data and I have repeated measures or matched pairs I would use…

Wilcoxon

If I am… Measuring a correlation and have ordinal or interval/ratio data I would use…

Spearman’s Rho

For 2 marks each…

1. Why has the psychologist chosen to use a Mann Whitney U test

2. Why has the psychologist chosen to use a Spearman’s rho

3. Why has the psychologist chosen to use a Chi squared test

4. Why has the psychologist chosen to use a Wilcoxon matched pairs

rank testThe Psychologist use a Spearman’s Rho because…

Reading the Tables…Higher or Lower??

On the Stats SheetHighlight:What type of data do they testDoes the observed value have to be LESS than or GREATER than the critical value

Higher or Lower…

Chi Squared

Higher or Lower…

Higher

Higher or Lower…

Mann U Whitney

Higher or Lower…

Lower

Higher or Lower…

Wilcoxon

Higher or Lower…

Lower

Higher or Lower…

Spearman’s Rho

Higher or Lower…

Higher

Higher or Lower… Whichever way you are looking; Higher or Lower

It will always mean the results are significant (or not)

P ≤ 0.05 You must ALWAYS write it like this!

Exam Q booklets – Find them!

Find every question that refers to significance,

statistical tests, type 1 & 2 errors

Finish Jan 2013 21, 22, 23

January 2012 21, 22, 23, 24