m of central tendency & measures of dispursion

• Mean

  Arithmetic average.

  1. Strength - sensitive measure. includes all the scores/values in the data set within the calculation. represents data set better than median or mode
  2. Limitation - may be unrepresentative. one very large or small number makes it distorted. the median or the mode tend not to be so easily distorted
• Median

  middle value

  1. Strength - less affected by extreme scores. the median is only focused on the middle value. in some cases may be more representative of the data set as a whole
  2. Limitation - less sensitive than the mean. the actual values of lower and higher numbers are ignored. extreme values may be important.
• Mode

  Most frequent/common value

  1. Strength - relevant to categorical data. when data is discrete sometimes the mode is the only appropriate measure.
  2. Limitation - an overly simple measure. the mode may be at one extreme. it is not a useful way of describing data when there are many modes.
• Range

  difference between highest and lowest value

  1. Strength - easy to calculate . arrange values in order and subtract smallest from largest. simple formula, easier than standard deviation
  2. Limitation - does not account for the disruption of scores. the range does not indicate whether most numbers are closely grouped around the mean or spread out evenly. the standard deviation is a much better measure of dispersion in this respect.
• Standard deviation

  measure of the average spread around the mean. the larger the standard deviation, the more spread out the data is.

  1. Strength - more precise than the range. includes all values within the calculation. therefore more accurate picture of the overall distribution of data set.
  2. Limitation - it may be misleading. can be distorted by extreme values. also, extreme values may not be revealed, unlike with the range.