Based on the data bellow, what would the effect size be?

Group one 12 and group two 11.
Standard deviation 3.

To calculate the effect size, you can use Cohen's d formula:

Effect Size (d) = (Mean Group 1 - Mean Group 2) / Standard Deviation

Given the information you provided:

Mean Group 1 = 12
Mean Group 2 = 11
Standard Deviation = 3

Plug these values into the formula:

Effect Size (d) = (12 - 11) / 3
Effect Size (d) = 1 / 3
Effect Size (d) ≈ 0.333

Therefore, the effect size would be approximately 0.333.