In a statistical experiment, an effect size is described as

Correct option is C

Effect size is a statistical concept that measures the magnitude of a treatment or experimental effect, regardless of sample size, to indicate the practical or clinical significance of the results. It is calculated by dividing the difference between the means of two groups by the standard deviation of the pooled groups or control group. The effect size provides a standardized measure of the strength of the relationship between variables or the extent of the difference between groups.