on your white boards… write an example of nominal data… write an example of ordinal data…...
TRANSCRIPT
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