Statistics Flashcards
What are descriptive statistics?
These describe the data and include:
- measure of central tendency: Mode, median, mean.
- measure of dispersion: the range.
Descriptive statistics include graphs and charts.
What are inferential statistics?
These draw inferences about the data, rather than merely describing them, and often involve the use of statistical tests such as:
- Spearman’s rank correlation coefficient (relationships and correlation)
- Mann-Whitney U test (differences)
- Chi squared (differences)
- Wilcoxon signed rank test (differences)
Alternative and experimental hypothesis look for either relationships or differences between variables.
Inferential stats (tests) examine whether the variables being studied are different or related enough to draw conclusions of that effect.
What is nominal data?
- in the form of categories/putting data into sets e.g. categorising answers as “yes” or “no” is putting them into categories.
- the Chi-squared test is a test of nominal data in terms of the detail of data; nominal data is the lowest level of measurement.
What is ordinal data?
- ranked data such as ratings (when data is out into a hierarchy).
- in terms of detail of data, ordinal data is the middle level of measurement.
What is interval data?
- data where real measurements are involved e.g. if temperature was recorded in degrees Celsius that would be interval/ratio data.
- interval/ratio data are scores that have equal intervals between them.
- inferential tests for interval/ratio data involve calculations because the data is mathematical.
- in terms of the amount of info provided, interval/ratio data is the highest level of measurement.
How do you choose which inferential test to use?
1) Test of a difference + nominal + independent groups = Chi-squared
2) Test of a difference + ordinal or interval + independent groups = Mann-Whitney U
3) Test of a difference + ordinal or interval + repeated measures = Wilcoxon
4) Test of a relationship + ordinal or interval = Spearman’s rank
