Question

mint plants
jack grew ten mint plants on his
back porch. he grew each plant in
its own pot, and each pot was the
same size and shape. jack noticed
that his plants did not grow many
leaves, and he wanted to see if
earthworms could help them grow
more. to test this idea, jack divided
his ten plants into two equal
groups. for one group, he added
three earthworms to the soil in each
pot. he did not add any earthworms
to pots in the other group.

two months later, jack counted the
number of leaves on each of the ten
plants. he compared the number of
leaves on the plants in each group.

complete the sentence.

in this experiment, the number of
earthworms was ______________.

a dependent variable

an independent variable

Explanation:

In an experiment, the independent variable is the factor that is manipulated or changed by the experimenter. Here, Jack manipulated the number of earthworms (adding 3 to one group and 0 to the other) to see its effect on plant growth (measured by number of leaves, the dependent variable). So the number of earthworms is the independent variable.

Answer:

an independent variable