The main output for this example is below. We would conclude that men and dogs do not significantly differ in the amount of dog-like behaviour they engage in. The confidence interval ranged from -5.495 to 7.895, which implies (assuming that this confidence interval is one of the 95% containing the true effect) that the difference between means in the population could be negative, positive or even zero. In other words, it’s possible that the true difference between means is zero. Therefore, this confidence interval confirms our conclusion that men and dogs do not differ in amount of dog-like behaviour. We can obtain the effect size as Cohen's d =0.12 [−0.51, 0.73] (below) and this shows a small effect with a very wide confidence interval that crosses zero. Again, assuming that this confidence interval is one of the 95% containing the true effect., the effect in the population could be negative, positive or zero.
| 95% CI for Mean Difference | 95% CI for Cohen's d | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| t | df | p | Mean Difference | SE Difference | Lower | Upper | Cohen's d | SE Cohen's d | Lower | Upper | |||||||||||||
| behaviour | 0.363 | 37.600 | 0.719 | 1.200 | 3.306 | -5.495 | 7.895 | 0.115 | 0.317 | -0.506 | 0.734 | ||||||||||||
| Note. Welch's t-test. | |||||||||||||||||||||||
| Group | N | Mean | SD | SE | Coefficient of variation | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| behaviour | Dog | 20 | 28.050 | 10.981 | 2.455 | 0.391 | |||||||
| Man | 20 | 26.850 | 9.901 | 2.214 | 0.369 | ||||||||
On average, men (M = 26.85, SE = 2.23) engaged in less dog-like behaviour than dogs (M = 28.05, SE = 2.455). However, this difference, 1.2, 95% CI [-5.495 to 7.895], was not significant, t(37.60) = 0.363, p = 0.719, and yielded a small effect Cohen's d =0.115 [−0.506, 0.734].