( ( Put ( ( ( the ( independent variable ) ) , ) ( which ( is ( ( ( controlled ( by ( the experimenter ) ) ) , ) ( on ( the ( x axis ) ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB Put) (NP (NP (DT the) (JJ independent) (NN variable)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (VP (VBN controlled) (PP (IN by) (NP (DT the) (NN experimenter))) (, ,) (PP (IN on) (NP (DT the) (JJ x) (NNS axis))))))))) (. .)))
Put the independent variable, which is controlled by the experimenter, on the x axis.
(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))))))))) (. .)))