Calculate Cohen's D:

Sample Mean Difference Score (time 1 - time 2) = 1.7
Standard Deviation Difference Scores = 3.2
Sample Size = 39

Question

Calculate Cohen's D:

Sample Mean Difference Score (time 1 - time 2) = 1.7
Standard Deviation Difference Scores = 3.2
Sample Size = 39

BlackTom AI · Accepted Answer

To start, identify the components needed for Cohen's d in a paired design: the mean difference and the standard deviation of the difference scores.

The given mean difference (time 1 minus time 2) is 1.7. The standard deviation of the difference scores is 3.2.

Cohen's d for paired data is calculated by dividing the mean difference by the standard deviation of the differences: d = mean_diff / SD_diff = 1.7 / 3.2.

Carrying out the division: 1.7 ÷ 3.2 ≈ 0.53125.

Rounding to two decimal places, the result is 0.53.

A note on interpretation: this effect size reflects the magnitude of change from time 1 to time 2 relative to the variability of those changes across participants. The computation hinges on using the SD of the difference scores rather than the pooled SD from independent groups, which is appropriate for paired measurements.

If you were to present multiple estimates, you might also report other forms of d or include confidence intervals, but the straightforward calculation here yields approximately 0.53.

Research Methods and Statistics in Psychology (1003PSY_3255)

Calculate Cohen's D: Sample Mean Difference Score (time 1 - time 2) = 1.7 Standard Deviation Difference Scores = 3.2 Sample Size = 39

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