Descriptive Statistics

• There are three measures of central tendency, the mean, mode and median. The median is the central value when arranged from lowest to highest. The mode is the most common value.
• Using the mean as a measure of central tendency ensures that all values are included which is representative of the whole data set, however it can be misleading if there are extreme values.
• Using the median as a measure of central tendency is easy to calculate and isn't affected by extreme values, however it is not very representative of the data set as a whole because it doesn't include all values.
• Using the mode as a measure of central tendency is reliable as it is unaffected by extreme values. It is the only method that can be used when data is in categories. However, it loses meaning when there is more than 1 mode.
• There are two measures of disperson; the range and statistical deviation. The range is the difference between the lowest and highest values. Statistical deviation is how much each value deviates from the mean. This is calculated by subtracting each value from the mean and then with this new set of data, calculate the mean of this second set.
• The range is an easy measure of dispersion to calculate, however it only takes into account the two most extreme values and therefore may be unrepresntative of the whole data set. It doesn't indicate whether it is closely group or spread around the mean.
• Statistical deviation is more precise than the range as it includes all values in the final calculation, however it can be distorted by extreme values.