descriptive statistics

• primary data is original data collected first hand
• secondary data is data that has already been collected and stored by someone else.
• primary data is more valid as it is specific to the purpose of the study
• primary data is more time consuming to collect, meaning we could end up with less data
• measures of central tendency is the typical average score from the data set (mode, median, mean)
• measures of dispersion is how spread out the scores in a data set are (range, standard deviation)
• the mean includes all scores but is affected by extreme scores
• the median and mode don’t include all scores but aren’t affected by extreme scores
• normal distributions- when the mean, median and mode are at the highest peak of the distribution
• positive skewed distribution- when the data is concentrated to the left, with the mode and median being below the mean
• to make a more normal distribution:

  1. adjust difficulty of test
  2. make it easier/ more difficult
  3. so more get a higher/ lower mark
  4. making a more normal distribution
• negatively skewed data is concentrated to the right with the mode and median being higher than the mean