An experiment was carried out to answer the question “Does the pH of water affect the
growth of radish plants?” Two groups of ten radish plants were set up. One group was
watered with water having a pH of 3.0, and the other group was watered with water having
a pH of 7.0. Both groups of plants received the same amount and intensity of light, the same
amount of water, and they were grown in the same type of soil. The heights of the radish
plants were measured every 2 days for a period of 2 weeks.
-- Which sentence is a possible hypothesis that was tested in this experiment?
(1) Does the pH of water affect the growth of radish plants?
(2) Will the amount of water alter the heights of the radish plants?
(3) The temperature of the water will affect the heights of the radish plants.
(4) The pH of the water will affect the heights of the radish plants.
-- What was the dependent variable in this experiment?
(1) heights of the plants (3) temperature of the water
(2) pH of the water (4) type of soil
-- Which activity might help to increase the validity of this experiment?
(1) repeating the experiment several times
(2) using two different types of radish seeds in each group
(3) using the same pH for both groups of plants
(4) placing one set of plants in sunlight and one in darkness