Measures of Central Tendency

The mean is the sum

The mean is the sum of all observations divided by the number of observations. For ungrouped data: x̄ = Σxi/n. For grouped data, we use three methods:

The median is the middle value

The median is the middle value when data is arranged in ascending or descending order. For odd number of observations: Median = (n+1)/2 th term. For e

The mode is the value

The mode is the value that appears most frequently in a dataset. For raw data, simply count frequencies. For grouped data, we identify the modal class

A bar graph where class intervals

A bar graph where class intervals are on x-axis and frequencies on y-axis, with no gaps between bars. The modal class appears as the tallest bar. Mode

A smooth curve plotting cumulative frequencies

A smooth curve plotting cumulative frequencies against class boundaries. 'Less than' ogive uses upper class boundaries and cumulative frequencies. Use