The confidence interval ranged from -1.45 to 0.01, which crosses zero suggesting that (if we assume that it is one of the 95% of confidence intervals that contain the true value) that the effect in the population could be zero. We also obtain a non-significant p-value, so we cannot conclude that there is a difference in listening numbers. We can obtain the effect size as d = -0.67 [-1.34, 0.01].
| 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 | |||||||||||||
| offer | -2.007 | 32.789 | 0.053 | -0.722 | 0.360 | -1.454 | 0.010 | -0.669 | 0.351 | -1.337 | 0.009 | ||||||||||||
| Note. Welch's t-test. | |||||||||||||||||||||||
| Group | N | Mean | SD | SE | Coefficient of variation | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| offer | Bon Scott | 18 | 3.278 | 1.179 | 0.278 | 0.360 | |||||||
| Brian Johnson | 18 | 4.000 | 0.970 | 0.229 | 0.243 | ||||||||
On average, more offers were made when listening to Brian Johnson (M = 4.00, SE = 0.23) than Bon Scott (M = 3.28, SE = 0.28). This difference, -0.722, 95% CI [-1.454, 0.010], was not significant, t(32.79) = -2.007, p = 0.053; but there was more than half a standard deviation difference between the groups, Cohen's d= -0.67 [-1.34, 0.01].