One member of each pair of dogs from the same litter was randomly assigned to a training group, and the other member of each pair was assigned to a no-training group. In other words, they were matched based on which litter they came from.

Below is SPSS output from a paired- (dependent-) samplesttest comparing the training to the no-training group on obedience test scores.

Paired Samples Statistics Sid. Error Mean N Std. Deviation Mean Training 16.50 12 2.067 597 No Training 11.50 12 2.431 702 Paired Samples Test Paired Differences 95% Confidence Interval of the Std. Error Difference Mean Std. Deviation Mean Lower Upper di Training - No training 5.000 2.296 663 3.541 6.459 7.543 11 1003