Descriptive statistics

• What is the term used for the large amount of data collected in psychological investigations?

  Raw data
• Why can raw data be overwhelming for psychologists?

  It can be hard to tell a clear story about what was found in a study
• What do descriptive statistics do?

  They summarize and describe features of a quantitative data set
• What are the two main categories of descriptive statistics?

  Measures of central tendency and measures of dispersion
• What are the measures of central tendency?

  The mean, median, and mode
• What do measures of dispersion refer to?

  How spread out the individual scores are in a data set
• What is the mode in a data set?

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

  It has two modes
• Why is the mode particularly useful for discrete numbers?

  It can provide a clear average for categories
• What is a criticism of the mode in small data sets?

  There may be multiple modes or no mode at all
• How is the median calculated?

  By ordering values and finding the middle score
• What is a positive aspect of using the median?

  It is not affected by extreme outlier scores
• What is a criticism of the median?

  Not all raw scores are used in its calculation
• How is the mean calculated?

  By adding all scores together and dividing by the number of scores
• What is a positive aspect of the mean?

  It uses all raw data in its calculation
• What is a criticism of the mean?

  It can be easily shifted by extreme values
• Why might a CEO choose to state the mean salary?

  To present the company in the best light
• What is the range in measures of dispersion?

  The difference between the largest and smallest values
• How is the range calculated?

  By subtracting the smallest value from the largest value
• What is a positive aspect of the range?

  It is easy to calculate
• What is a criticism of the range?

  Extreme scores can distort its value
• What does the standard deviation indicate?

  How spread out or clustered the scores are around the mean
• What is a key characteristic of the standard deviation?

  The larger the standard deviation, the more spread out the scores
• What is a positive aspect of the standard deviation?

  It includes all values in its calculation
• What is a criticism of the standard deviation?

  It can be distorted by extreme values
• What is the formula to calculate a percentage?

  Percentage = (part/whole) × 100
• What is the first step in calculating the percentage of a subgroup?

  Write the fraction of the subgroup over the total population
• How do you convert a fraction to a percentage?

  Divide the fraction and multiply by 100
• How do you find the percentage of a number?

  Convert the percentage to a decimal and multiply by the number
• What does a negative percentage change indicate?

  There has been a decrease in the number
• What are correlations in descriptive statistics?

  They describe the relationship between two variables
• What are the types of correlations?

  Positive, negative, and zero correlations
• What is the correlation coefficient?

  A numerical value that indicates the strength and direction of a correlation
• Why is careful selection of descriptive statistics important?

  It can influence how data is perceived and interpreted
• What are the strengths and weaknesses of the mean, median, and mode?

  • Mean:
  • Strength: Uses all raw data
  • Weakness: Sensitive to extreme values
  • Median:
  • Strength: Not affected by outliers
  • Weakness: Does not use all raw scores
  • Mode:
  • Strength: Useful for discrete numbers
  • Weakness: May have multiple modes or none in small data sets
• What are the strengths and weaknesses of the range and standard deviation?

  • Range:
  • Strength: Easy to calculate
  • Weakness: Distorted by extreme scores
  • Standard Deviation:
  • Strength: Includes all values
  • Weakness: More complex to calculate and distorted by extreme values
• How do you calculate the percentage of each subgroup in a sample?

  1. Write the fraction of the subgroup over the total population.
  2. Convert the fraction to a decimal.
  3. Multiply by 100 to get the percentage.
• How do you calculate the percentage change between two numbers?

  1. Subtract the old number from the new number.
  2. Divide by the old number.
  3. Multiply by 100 to get the percentage change.
• What is the importance of understanding correlations in statistics?

  • Helps to identify relationships between variables
  • Aids in predicting outcomes based on data
  • Essential for interpreting research findings