Data from Gelman & Weakliem (2009). The researchers recorded the number of daughters and sons for each celebrity (repeated-measures design).
| 95% CI for Cohen's d | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Measure 1 | Measure 2 | t | df | p | Cohen's d | SE Cohen's d | Lower | Upper | |||||||||||
| sons | - | daughters | 0.807 | 253 | 0.420 | 0.065 | 0.081 | -0.058 | 0.189 | ||||||||||
| Note. Cohen's d corrected for correlation between observations. | |||||||||||||||||||
| Note. Student's t-test. | |||||||||||||||||||
| N | Mean | SD | SE | Coefficient of variation | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| sons | 254 | 0.677 | 0.901 | 0.057 | 1.331 | ||||||
| daughters | 254 | 0.618 | 0.902 | 0.057 | 1.460 | ||||||
Looking at the output above, we can see that there was a non-significant difference between the number of sons and daughters produced by the ‘beautiful’ celebrities.
The Paired Samples T-Test table shows Cohen’s d = 0.07. This means that there is 0.07 of a standard deviation difference between the number of sons and daughters produced by the celebrities, which is a near-zero effect.
In this example the output tells us that the value of t was 0.81, that this was based on 253 degrees of freedom, and that it was non-significant, p = .420. We also calculated the means for each group. We could write this as follows:
There was no significant difference between the number of daughters (M = 0.62, SE = 0.06) produced by the ‘beautiful’ celebrities and the number of sons (M = 0.68, SE = 0.06), t(253) = 0.81, p = .420, d = 0.07.