Research methodsLesson 3 of 4 in the course Evaluation and evidence

Effect Sizes: Estimation, Standardization, and Common Measures

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

Save course
Lesson progress
0 / 5

Your progress is kept in this browser only.Sign up to save it

Summary

Effect size describes how large a phenomenon or relationship is, and sometimes its direction. It matters because a result can be statistically significant yet too small to be practically important.

An effect size is a quantitative measure of the magnitude—and often the direction—of a phenomenon. Depending on the context, the term can refer to an observed statistic calculated from a sample, a parameter describing a hypothetical population, or the equation used to calculate that measure.

All flashcards

What is an effect size?
A quantitative measure of the magnitude, and often the direction, of a phenomenon or relationship.
How do population and sample effect sizes differ?
A population effect describes the target population; a sample effect is calculated from observed data to estimate it.
What does squaring Pearson's correlation coefficient remove?
It removes the sign, so the squared coefficient does not indicate whether the relationship is positive or negative.
Why might researchers use standardized effects?
They allow results measured on different scales to be compared or combined.
How does Hedges' gg differ from Cohen's dd?
It applies a small-sample correction to reduce bias in the standardized mean difference.

Quiz questions

  1. What does a hypothesis test address, as distinct from an effect size?Answer: Whether the observed data are compatible with a specified null hypothesis under the test.
  2. For two independent groups, what does Cohen's dd conventionally use to standardize the mean difference?Answer: A pooled standard deviation from the two groups.
  3. How does omega-squared generally compare with eta-squared as an estimate of variance explained?Answer: Omega-squared is a less biased alternative to eta-squared.
  4. A probability-of-superiority value of 0.92 is commonly interpreted as what?Answer: A 92% chance that a randomly selected value from one group exceeds one from the other.
  5. What does Cliff's delta compare for two distributions?Answer: The frequency of values from one distribution exceeding, versus falling below, values from the other.

Based on the Wikipedia article Effect size, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

More in Research methods

All Research methods lessons
Research methodsSurvey Methodology: Sampling, Measurement, Response, and Data Quality5 flashcards · 5 quiz questions · 4 gamesPlay free →Research methodsMeasurement Scales, Rounding, and Frequency Tables5 flashcards · 5 quiz questions · 4 gamesPlay free →Research methodsObservational Studies: Designs, Bias, and Causal Inference5 flashcards · 5 quiz questions · 4 gamesPlay free →Research methodsSystematic Reviews: Methods, Reporting, Applications, and Limitations5 flashcards · 5 quiz questions · 4 gamesPlay free →Research methodsMeasurement Reliability: Classical Test Theory, Estimation, and Precision5 flashcards · 5 quiz questions · 4 gamesPlay free →Research methodsEthical Review and Participant Protection in Human and Animal Research5 flashcards · 5 quiz questions · 4 gamesPlay free →