Descriptive Statistics

• What do descriptive statistics do?

  They summarize and describe data
• Why should descriptive statistics be easily understood?

  To avoid further questions from readers
• What are the types of descriptive statistics to know for the exam?

  • Measures of Central Tendency (mean, median, mode)
  • Measures of Dispersion (range, standard deviation)
  • Graphical representations (bar chart, histogram, tables)
  • Percentages
  • Correlations (positive, negative, zero)
• What is the mean in descriptive statistics?

  The average of all the scores
• How do you calculate the mean?

  Add all scores and divide by count
• What is an advantage of using the mean?

  It uses all scores in the data set
• What is a disadvantage of the mean?

  It can be distorted by extreme scores
• What is the median in descriptive statistics?

  The central number in a set of scores
• How do you calculate the median?

  Rank values and find the middle score
• What is an advantage of the median?

  Not affected by extreme scores
• What is a disadvantage of the median?

  Not as sensitive as the mean
• What is the mode in descriptive statistics?

  The most common score in a set
• What does it mean if data is bimodal?

  It has two modes
• What is an advantage of the mode?

  Not affected by extreme values
• What is a disadvantage of the mode?

  Not as sensitive as the mean
• How do you choose which measure of central tendency to use?

  • Use the mean for accuracy unless extreme scores exist
  • Use the median if extreme scores are present
  • Avoid the mode if data is bimodal or has no modal score
  • Avoid the median if data is skewed
• What do measures of dispersion indicate?

  How spread out the data is
• What does the range measure?

  How spread out a set of scores is
• How do you calculate the range?

  Subtract lowest value from highest value
• What is an advantage of the range?

  Easier to calculate than standard deviation
• What is a disadvantage of the range?

  Gives no information on score clustering
• What does standard deviation measure?

  How far scores are from the mean
• What does a large standard deviation indicate?

  A wide spread of scores away from the mean
• What does a small standard deviation indicate?

  Scores are close together around the mean
• What is an advantage of standard deviation?

  All scores are used in its calculation
• What is a disadvantage of standard deviation?

  More time-consuming to calculate than range
• What are the key measures of central tendency?

  • Mean
  • Median
  • Mode
• What are the key measures of dispersion?

  • Range
  • Standard Deviation