调查回复率计算器
使用此调查回复率计算器快速获得准确的计算结果。
Cohen's d
0.543
Cohen's d vs Group 1 Mean
公式
How Cohen's d Measures Effect Size
Cohen's d quantifies the difference between two group means in standard deviation units, providing a measure of practical significance independent of sample size.
Formula
d = Mean_1 - Mean_2
Where SD_pooled = sqrt((SD_1^2 + SD_2^2) / 2)
Interpretation
In education research, an effect size of 0.4 or higher is generally considered practically significant.
计算示例
Treatment group scored mean 78 (SD = 10), control group scored mean 72 (SD = 12).
- 01Pooled SD = sqrt((100 + 144) / 2) = sqrt(122) = 11.05
- 02Mean difference: |78 - 72| = 6
- 03Cohen's d = 6 / 11.05 = 0.543
- 04Interpretation: Medium effect size
常见问题
Why not just use p-values?
P-values indicate statistical significance but not practical importance. A large sample can make a tiny difference statistically significant.
What is a meaningful effect size in education?
Hattie suggests d = 0.4 as the threshold for a worthwhile intervention in education (the "hinge point").
Can effect size be negative?
This calculator reports the absolute value. A negative d would simply mean Group 2 scored higher than Group 1.