Measures of central tendency

• Measures of central tendency inform us about central or middle values for a set of data. They are averages - ways of calculating a typical value for a set of data
• Mean

  Calculated by adding up all the data items and dividing by the number of data items. It can only be used with ratio and interval level data.
• Median

  Middle value in an ordered list. All data iteams must be arranged in order and central value is then the median. If there are an even number of data items there will be two central values to calculate median add two data items and divide by 2. Median can be used with ratio interval and ordinal data
• Mode

  Value that is the most common data item. With nominal data it is the category that has the highest frequency . With interval and ordinal it is the data that occurs the most frequently . To identify this the data items need to be arranged in order. Bi modal is when two numbers have the same frequency
• Mean

  S: Most sensitive measure of central tendency because it takes into account exact distance between all values of data. L: Sensitivity means it can be easily distorted by one or few extreme variables (misrepresentative)

  Cannot be used with nominal data
• Median

  S: Not affected by extreme scores do it can be useful. Appropriate for ordinal data.

  Easier to calculate

  L : less sensitive as not all values are considered
• Mode

  S : Only method that can be used when data are in categories (nominal)

  L : not useful way of describing data when there are several modes