the results obtained across different partitions (although individually unbiased) will be correlated. Meta-analysis standard errors will therefore be anticonservative, and this bias can be substantial (see Methods). Therefore, to maximize the usefulness of our PGIs for research involving related individuals or brain-scan data, we assigned to the same partition all pairs of individuals that are related up to second degree (and some pairs of third degree), as well as all individuals with brain-scan data.
