Eta Squared Calculator
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Eta Squared (η²) is a measure of effect size used in the analysis of variance (ANOVA) to indicate the proportion of total variance that is attributed to a specific factor. Understanding this metric helps researchers assess the strength of an effect in experimental studies.
Historical Background
Eta Squared has been widely used in statistical analysis, especially in psychological and educational research, since the mid20th century. It serves as a valuable measure to interpret the practical significance of findings in addition to their statistical significance.
Calculation Formula
The formula to calculate Eta Squared is as follows:
\[ \eta^2 = \frac{\text{SS}{\text{effect}}}{\text{SS}{\text{total}}} \]
Where:
 SS_{effect}: Sum of Squares for the effect
 SS_{total}: Total Sum of Squares
Example Calculation
If SS_{effect} = 20 and SS_{total} = 100, then:
\[ \eta^2 = \frac{20}{100} = 0.2 \]
This means that 20% of the total variance can be explained by the effect being studied.
Importance and Usage Scenarios
Eta Squared is crucial in research where the magnitude of an effect needs to be communicated clearly. It is especially useful in fields like psychology, where the size of an effect can provide insights into the practical implications of experimental results.
Common FAQs

What is a good Eta Squared value?
 Values closer to 1 indicate a larger effect size. There is no strict threshold, but generally, η² values of 0.01, 0.06, and 0.14 are considered small, medium, and large effects, respectively.

Is Eta Squared the same as R Squared?
 No, they are different. While both are measures of explained variance, R Squared is typically used in regression analysis, whereas Eta Squared is used in ANOVA.

Can Eta Squared be negative?
 No, since it is a proportion of variance, Eta Squared cannot be negative.