Effects Sizes and Confidence Intervals

A comprehensive set of vocabulary flashcards covering key concepts related to effect sizes and confidence intervals.

Confidence Intervals

Communicates precision by providing a range of plausible values for the population parameter being estimated.

Effect Sizes

Communicates strength by telling us the magnitude of the experimental effect, or relationship between variables.

Statistical Significance Testing

Communicates probability by telling us how likely the current result would be if the study’s null hypothesis were true.

Cohen’s d

A measure estimating the magnitude of standardized differences between two groups means.

Hedges’ g

A measure similar to Cohen’s d, but more appropriate for small sample sizes due to its bias correction.

Pearson’s r

Measures the strength of a linear relationship between continuous variables.

Odds Ratio

The ratio of the probability that an outcome occurs to the probability that the outcome does not occur.

Point-Biserial Correlation

Measures the strength of the relationship between one dichotomous variable and one continuous variable.

Small Effect Size

Cohen's d or Hedges' g value ranges approximately from +/- 0.2.

Medium Effect Size

Cohen's d or Hedges' g value ranges approximately from +/- 0.5.

Large Effect Size

Cohen's d or Hedges' g value ranges approximately from +/- 0.8.

Confidence Level

Researchers commonly use levels of either 95% or 99% to calculate confidence intervals.

Confidence Interval (CI) Example

An example would be an odds ratio of 7.5 with a confidence interval expressed as 95% CI [5.32, 10.45].

Precision in Confidence Intervals

Relatively smaller CIs suggest more precision and relatively large CIs suggest less precision.

No Effect in CI

If 0 falls between the lower and upper limits of a CI for a mean difference or correlation, we cannot conclude the effect is real.

Establishing Confidence Intervals

Establishes whether an effect occurred, the possible range of scores if tested with other samples, and the effect's potential positivity or negativity.