( ( ( ( Independent variable ) -- ) ( ( A factor ) ( in ( ( ( ( ( ( an experiment ) ( that ( ( the experimenter ) ( systematically manipulates ) ) ) ) , ) ( also ( a ( certain trait ) ) ) ) or ) ( characteristic ( ( ( possessed ( by ( a subject ) ) ) and ) ( selected ( by ( the experimenter ) ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (JJ Independent) (NN variable)) (: --) (NP (NP (DT A) (NN factor)) (PP (IN in) (NP (NP (NP (DT an) (NN experiment)) (SBAR (IN that) (S (NP (DT the) (NN experimenter)) (ADVP (RB systematically)) (VP (VBZ manipulates))))) (, ,) (NP (ADVP (RB also)) (DT a) (JJ certain) (NN trait)) (CC or) (NP (NP (NN characteristic)) (VP (VP (VBN possessed) (PP (IN by) (NP (DT a) (NN subject)))) (CC and) (VP (VBN selected) (PP (IN by) (NP (DT the) (NN experimenter))))))))) (. .)))
Independent variable-- A factor in an experiment that the experimenter systematically manipulates, also a certain trait or characteristic possessed by a subject and selected by the experimenter.
(ROOT (S (NP (NP (DT The) (NNS values)) (PP (IN of) (NP (JJ independent) (NNS variables)))) (VP (VBP are) (VP (VBN controlled) (PP (IN by) (NP (NP (DT the) (NN experimenter)) (PP (IN over) (NP (NP (DT the) (NN course)) (PP (IN of) (NP (DT an) (NN experiment))))))))) (. .)))