Data from Tuk et al. (2011). The authors investigated how increased urination frequency facilitates impulse control in other domains, unrelated to bladder control.
| 95% CI for Cohen's d | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| t | df | p | Cohen's d | SE Cohen's d | Lower | Upper | |||||||||
| ll_sum | 2.203 | 100 | 0.030 | 0.436 | 0.203 | 0.042 | 0.828 | ||||||||
| Note. Student's t-test. | |||||||||||||||
| Group | N | Mean | SD | SE | Coefficient of variation | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ll_sum | High urgency (drink everything) | 50 | 4.500 | 1.594 | 0.225 | 0.354 | |||||||
| Low urgency (take sips from the water) | 52 | 3.827 | 1.491 | 0.207 | 0.390 | ||||||||
Looking at the means in the Group Descriptives table above, we can see that on average more participants in the High Urgency group (M = 4.5) chose the large financial reward for which they would wait longer than participants in the Low Urgency group (M = 3.8). Looking at the Independent Samples T-Test table, we can see that this difference was significant, p = .03.
The Independent Samples T-Test table shows the effect size, and we get d = 0.44. In other words, the number of rewards chosen by the high urgency group was almost half a standard deviation more than the number chosen by the low urgency group. However the confidence interval is very wide. If the confidence interval is one of the 95% that contain the true parameter value, then the effect could be as small as 0.04 (i.e., basically zero) or as large as 0.83 (i.e., huge).
On average, participants who had full bladders (M = 4.5, SD = 1.59) were more likely to choose the large financial reward for which they would wait longer than participants who had relatively empty bladders (M = 3.8, SD = 1.49), t(100) = 2.20, p = .03. This effect equates to almost a half standard deviation difference, d = 0.44, 95% CI [0.04,0.83].