descriptive statistics

measures of central tendency

• mean

• median

• mode

measures of dispersion

• range

• standard deviation

mean strength

• most sensitive measure

• takes account of the exact distance between all values of the data

mean weakness

• sensitivity means it be easily distorted by one extreme value

• end up being less representative of the data as a whole

median strength

• not affected by extreme scores

• can be useful under such circumstances

median weakness

• may produce ‘nonsense’ value 

• not in the original data set

mode strength

value will definitely be in the data set

mode weakness

not a useful way of describing data when there are several modes

range strength

• relatively easy to calculate in comparison to standard deviation

range weakness

• is affected by extreme values

• they may not reflect the data set accurately

standard deviation strength

• precise measure of dispersion

• know whether values are closely grouped or spread out around the mean

standard deviation weakness

• may hide characteristics of data

• only indicates how far each value is from the mean