Power Analysis Flashcards
What is statistical power?
The probability of detecting a true population effect, given a particular sample.
What are the 3 factors that determine the power of a study?
- Alpha level
- Sample size
- Effect size
What is one of the most useful aspects of power analysis?
The estimation of the sample size required for a study
What are the 2 measures of effect size for measures of association?
- Eta-squared
- R-squared
What is the measure of effect size for measures of difference?
Cohen’s d
What is Eta-squared?
The proportion of variance in a DV explained by a single IV.
What is Partial Eta-squared?
Estimates a specific effect size if there is more than one IV.
What is R-squared?
1 - the proportion of unexplained variance.
What is Cohen’s d?
When there are only two groups, 𝒅 is a ratio of the difference between the two groups with their error variance.
What statistical test has significantly larger effect sizes?
Cohen’s d.
Small: 0.2-0.3
Medium: 0.3-0.5
Large: 0.5 or larger
What are the 2 ways to decide what effect size is being aimed for?
- Based on previous research
- Based on theoretical importance
What is the name of the software that can be used to estimate the minimal sample size we would need to obtain a specific power level?
G*Power.
If we wanted 80% power, we would input effect size, alpha, and _________ into G*Power to get our sample size estimate.
1−𝛽=0.8.
Why is reporting effect size important?
It aids future attempts to replicate/extend your findings.
