Measures of central tendency
Add all the measurements together then divide by the number of measurements taken.
Arrange the data in order, and take the middle value as the median.
The value which occurs most often.
Measures of dispersion
The spread of data around the average.
Range is the distance between the highest and lowest value.
Example: 12 17 21 23 24 24 25 26 29 31
Range = 12–31
Interquartile range is the part of the range that covers the middle 50% of the data.