Research Psych

  1. Measure of Variability
    • Measures of variability describe the extent
    • to which scores in a distribution differ from each other
  2. The Range
    • The range indicates the distance
    • between the two most extreme scores in a distribution
  3. Variance and Standard Deviation
    • two measures of variability that indicate
    • how much the scores are spread out around the mean

    • •We use the mean as our reference point since
    • it is at the center of the distribution
  4. SampleVariance
    / Sample Standard Deviation
    • sample variance is the average of the squared deviations of
    • scores around the sample mean

  5. Computational Formula:
  6. Population Variance
  7. Population Standard Deviation
  8. Estimated Population Variance
    • By dividing the numerator of the sample
    • variance by N - 1, we have an unbiased
    • estimator of the population variance

  9. Estimated Population Variance
    Computational formula
  10. Estimated Population Standard Deviation
    • By dividing the numerator of the sample
    • standard deviation by N - 1, we have an unbiased
    • estimator of the population standard deviation.

  11. Unbiased Estimators
    • 1.
    • 2.
    • Quantity N-1 is called the degrees of freedom
  12. Proportion of Variance Accounted For
    • proportion of variance accounted for is the proportion of
    • error in our predictions when we use the overall mean to predict scores that is eliminated when we use the relationship with another variable to predict scores
Card Set
Research Psych
Psych Exam