they might be but not at not at the human factors level
( they ( might ( be ( ( but ( ( not ( at not ) ) ( at ( the ( human factors ) ) ) ) ) level ) ) ) )
(ROOT (S (NP (PRP they)) (VP (MD might) (VP (VB be) (ADJP (PRN (CC but) (ADVP (RB not) (IN at) (RB not)) (PP (IN at) (NP (DT the) (JJ human) (NNS factors)))) (JJ level))))))
They are actually at the human factors level. 
( They ( ( ( are actually ) ( at ( the ( human ( factors level ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (ADVP (RB actually)) (PP (IN at) (NP (DT the) (JJ human) (NNS factors) (NN level)))) (. .)))