Descriptive statistics

Two aspects of single variables (univariate) should be graphed and described:
 * 1) Central tendency
 * 2) 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.

Normally distributed variables
For normally distributed variables:
 * 1) Descriptive statistics:
 * 2) Central tendency: mean, median, mode
 * 3) Spread: standard deviation, skewness and kurtosis,  range, inter-quartile range, percentiles, minimum and maximum.
 * 4) Graphs:
 * 5) histogram
 * 6) box plot

Non-normally distributed variables
For non-normally distributed variables:
 * 1) Descriptive statistics:
 * 2) Central tendency: frequencies, percentages, mode
 * 3) Spread: range, inter-quartile range, percentiles, minimum and maximum
 * 4) Graphs: bar chart, pie chart