Remember that confidence intervals are constructed such that in 95% of samples the intervals contain the true value of the mean difference. So, assuming that this sample’s confidence interval is one of the 95 out of 100 that contain the population value, we can say that the true mean difference lies between −1.83 and −0.67. The importance of this interval is that it does not contain zero (both limits are negative), which tells us that the true value of the mean difference is unlikely to be zero.
