Descriptive statistics + data presentation

• Measures of central tendency:

  reduces a large amount of data to a single value

  three measure:

  • MEAN - sharing out evenly of data - statistical average
  • MEDIAN - central value
  • MODE - most frequent score
• Measures of dispersion:

  Both show the spread of data

  • RANGE - highest score-lowest score: if range is high then this shows there is a wide spread of data + if low shows results are similar
  • STANDARD DEVIATION - consistency: number which reflects the spread of scores + how far these deviate either side of the mean + large number shows scores were inconsistent
• Distributions:

  • Normal - mean, mode + median are all located at the highest peak - creates symmetrical spread of frequency data
  • Positive skew - Peak leans left + if mean is higher than mode = positive (students have performed poorly in test) mode, median, mean
  • Negative skew - peak leans right + if mean is lower than mode = negative (students performed well in test) mean, median mode

  mode is always the peak