This is an observational study, and you may be analyzing it as a designed one. There was no randomization, no large scale matched control group per se—that wasn’t the intention. The intention is to analyze a specific population, and compare it to the existing literature on prevalence of mutations. That’s how these things are done, you have to use the citations given to understand the broader context of a study. One study is not useful on its own.
Also, there’s this—they did hypothesis tests against a control group:
> Variants (SNP/ InDel) generated with this method were compared with a normal dataset using Archer’s analysis pipeline to distinguish noise from a true call. The normal dataset was created with sequencing data from seven young, healthy individuals.