The main limitation of this approach is that there are likely to be differences between the two groups that can not be controlled for, such as school or class. (educationendowmentfoundation.org.uk)
It is therefore important to understand the potential benefits and the possible limitations of the approach. (educationendowmentfoundation.org.uk)
Another regrettable limitation of this approach is that it doesn't offer a complete picture of the somatic mutations beyond nonsynonymous - coding events. (massgenomics.org)