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Cohen's d Effect Size Calculator

Calculate Cohen's d — the standardized difference between two group means in pooled standard deviation units. Measures how big an effect is, not just whether it is significant.

Group 1 Mean

Group 2 Mean

Group 1 Standard Deviation

Group 2 Standard Deviation

Probability

Confidence Interval Calculator

Computes the range of values likely to contain a true population mean at your chosen confidence level. Use it when reporting survey results, clinical trial outcomes, or any estimate derived from a sample.

Sample Mean

Sample Standard Deviation

Sample Size (n) (observations)

Confidence Level

Distribution Type

Key differences

	Cohen's d Effect Size Calculator	Confidence Interval Calculator
Category	Statistics	Probability
Inputs required	4	5
Result	Cohen's d	Margin of Error (±)
What it does	Calculate Cohen's d — the standardized difference between two group means in pooled standard deviation units. Measures how big an effect is, not just whether it is significant.	Computes the range of values likely to contain a true population mean at your chosen confidence level. Use it when reporting survey results, clinical trial outcomes, or any estimate derived from a sample.