Descriptive Statistics

• What is the term for the data collected in psychological investigations?

  Raw data
• Why are descriptive statistics important in psychology?

  They summarize and clarify large data sets
• What do descriptive statistics summarize?

  Features of a quantitative data set
• What are the two main types of descriptive statistics?

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

  Mean, median, and mode
• What do measures of dispersion indicate?

  How spread out individual scores are
• 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 useful for discrete numbers?

  It provides a clear average for categories
• What is a criticism of the mode?

  It may not provide a clear average in small sets
• How is the median calculated?

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

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

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

  Add all scores and divide by the number
• 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 skewed by extreme values
• Why might a CEO choose to state the mean salary?

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

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

  Subtract the smallest value from the largest
• What is a criticism of the range?

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

  How spread out scores are around the mean
• 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
• How can percentages be expressed?

  As fractions or decimals
• What is the first step in calculating a percentage of a number?

  Convert the percentage to a decimal
• How do you calculate the percentage of 595 out of 2480?

  Divide 595 by 2480 and multiply by 100
• How do you find 24% of 250?

  Multiply 0.24 by 250
• How do you calculate percentage change?

  Subtract old number from new, divide, then multiply by 100
• What does a negative percentage change indicate?

  A decrease in the number
• What are correlations in descriptive statistics?

  Relationships between two variables
• What does a positive correlation indicate?

  As one variable increases, the other also increases
• What does a negative correlation indicate?

  As one variable increases, the other decreases
• What is the correlation coefficient?

  A numerical value indicating the strength of a correlation
• Why is careful selection of descriptive statistics important?

  To avoid misrepresentation of data
• What are the steps to calculate percentages?

  1. Convert percentage to decimal
  2. Multiply by the total number
  3. For percentage change:

  • Subtract old from new
  • Divide by old
  • Multiply by 100
• What are the types of correlations?

  • Positive correlation: Both variables increase together
  • Negative correlation: One variable increases while the other decreases
  • Zero correlation: No relationship between variables