Question

Bromeliads are tropical flowering plants. Many are epiphytes that attach to trees and obtain moisture and nutrients from air and rain. Their leaf bases form cups that collect water and are home to the larvae of many insects. In an experiment in Costa Rica, Jacqueline Ngai and Diane Srivastava studied whether added nitrogen increases the productivity of bromeliad plants. Bromeliads were randomly assigned to nitrogen or control groups. The table contains the data on the number of new leaves produced over a seven‑month period.

Control	1111	1313	1616	1515	1515	1111	1212
Nitrogen	1515	1414	1515	1616	1717	1818	1717	1313

Is there evidence that adding nitrogen increases the mean number of new leaves formed?

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You may find Table C helpful.

STATE: Is there evidence that adding nitrogen increases the mean number of new leaves formed?

PLAN: Let ?1μ1 be the mean number of new leaves on plants from the control population, and ?2μ2 be the mean for the nitrogen population.

State the null and alternative hypotheses.

?0:?1=?2H0:μ1=μ2 versus ??:?1≠?2Hα:μ1≠μ2

None of the other choices are correct.

?0:?1=?2H0:μ1=μ2 versus ??:?1>?2Hα:μ1>μ2

?0:?1=?2H0:μ1=μ2 versus ??:?1<?2Hα:μ1<μ2

SOLVE: Find the ?t statistic. (Enter your answer rounded to three decimal places.)

?=t=

Find the ?P ‑value.

0.05<?<0.10.05<P<0.1

0.01<?<0.050.01<P<0.05

?<0.01P<0.01

?>0.1P>0.1

CONCLUDE: We have

no evidence that nitrogen increases the mean number of new leaves found.

weak evidence that nitrogen increases the mean number of new leaves found.

None of the other choices are correct.

strong evidence that nitrogen increases the mean number of new leaves found.

Answer 1