Two aspects of single variables (univariate) should be graphed and described:
- Central tendency
- Shape and spread of the data distribution
The choice of which graphs and descriptive statistics to use depends on the level of measurement and whether the variable is normally distributed.
For normally distributed variables:
- Descriptive statistics:
- Central tendency: mean, median, mode
- Spread: standard deviation, skewness and kurtosis, range, inter-quartile range, percentiles, minimum and maximum.
- Graphs:
- histogram
- box plot
For non-normally distributed variables:
- Descriptive statistics:
- Central tendency: frequencies, percentages, mode
- Spread: range, inter-quartile range, percentiles, minimum and maximum
- Graphs: bar chart, pie chart