Descriptive statistics

• Measures of central tendency

  Any measure of the average value in a set of data, including mean, median, and mode
• Descriptive statistics

  Use of graphs, tables, and summary statistics to identify trends and analyze sets of data
• Mean

  Arithmetic average of a set of values
• How is the mean calculated?

  By adding up all of the scores or value in a set of data and dividing by the total number of scores there are
• Median

  Central value in a set of data when values are arranged from lowest to highest - middle number in an odd number of scores, and the number halfway between two middle scores in an even number of scores
• Mode

  The most frequently occurring value in a set of data
• What is a bi-modal data set?

  A data set with two modes
• When do some data sets not have a mode?

  If all the scores are different
• When are modal groups identified?

  When wanting to find out the most popular thing
• Measures of dispersion

  Measures of the spread or variation in a set of scores, based on how much scores vary, including the range and standard deviation
• Range

  Simple calculation of the spread of scores
• How is the range calculated?

  By taking the lowest value away from the highest value and adding 1 as a mathematical correction
• Why is adding 1 to the range important?

  It allows for the fact that raw scores are often rounded up or down when recorded within research
• Standard deviation

  Sophisticated measure of dispersion which tells us how far scores deviate (move away) from the mean - the larger the standard deviation, the greater the dispersion
• What does a large standard deviation suggest in experiments?

  Not all participants were affected by the independent variable in the same way, and there could be a few anomalous results
• What does a low standard deviation reflect?

  Data is tightly clustered around the mean, meaning all participants respond in a similar way