Measures of central tendency

• What is the mean?


  Add up all data items and divide by number of data items. Only used with ratio & interval data.
• What are measures of central tendency?

  Averages- inform us of central values for set of data. Descriptive statistic
• What is the median?

  Middle value in ordered data list. Used with ratio, interval & ordinal data.
• What is the mode?


  Value that's most common data item. Used with nominal, interval and ordinal data.
• Evaluate mean:


  Most sensitive measure as it takes account of exact distance between all values of all data. Easily distorted by extreme values & thus misrepresentative of data as a whole. Can't be used with nominal data or discrete data.
• Evaluate median:


  Not affected by extreme values so useful under such circumstances. Used with ordinal data & easier to calculate. Not as sensitive as mean as exact values not reflected in median.
• Evaluate mode:


  Unaffected by extreme values & more useful for discrete data & is only method that can be used with nominal data. Not useful way of describing data when there's several modes.