(S (S (BASENP (DT The) (NNS results)) (VP (VBP have) (NP (BASENP (DT a) (NN margin)) (PP (IN of) (NP (BASENP (NN sampling) (NN error)) (PP (IN of) (BASENP (NN +) (CC /) (NN -) (NN 2.9)))))))) (PERIOD .))