( Experiments ( ( are ( controlled ( through ( ( ( ( ( the use ) ( of ( independent variables ) ) ) ( -LRB- ( ( which ( can ( be ( changed ( by ( the experimenter ) ) ) ) ) ) -RRB- ) ) ) and ) ( ( dependent variables ) ( -LRB- ( ( which ( are ( changes ( dependent ( on ( changes ( in ( the ( independent variable ) ) ) ) ) ) ) ) ) -RRB- ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Experiments)) (VP (VBP are) (VP (VBN controlled) (PP (IN through) (NP (NP (NP (DT the) (NN use)) (PP (IN of) (NP (JJ independent) (NNS variables)))) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT which)) (S (VP (MD can) (VP (VB be) (VP (VBN changed) (PP (IN by) (NP (DT the) (NN experimenter)))))))) (-RRB- -RRB-)) (CC and) (NP (NP (JJ dependent) (NNS variables)) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (NP (NP (NNS changes)) (ADJP (JJ dependent) (PP (IN on) (NP (NP (NNS changes)) (PP (IN in) (NP (DT the) (JJ independent) (NN variable)))))))))) (-RRB- -RRB-))))))) (. .)))
Experiments are controlled through the use of independent variables (which can be changed by the experimenter) and dependent variables (which are changes dependent on changes in the independent variable).
(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))))))))) (. .)))