Homogeneous

/ˌhoʊməˈdʒiːniəs/ adjective hard

Made up of parts or members that are all alike, without much variation.

The sample group was fairly homogeneous, which limited how broadly the findings could be generalized.

Memory Trick

Greek 'homo-' (same) plus 'genos' (kind) — a homogeneous group is the 'same kind' all the way through.