3. after studying about recycling, members of john’s biology class investigated the effects of various recycled products on plant growth. john’s lab group compared the effect of different aged grass compost on bean plants. because decomposition is necessary for the release of nutrients, the group hypothesized that older grass compost would produce taller bean plants. three flats of bean plants (25 per flat) were grown for 5 days. the plants were then fertilized as follows: flat a = 450. g of 3 month old compost; flat b = 450. g of 6 month old compost; flat c = 0 g of compost. the plants received the same amount of sunlight and water each day. at the end of 30 days, the group recorded the height of the plants in cm.

hypothesis:
independent variable:
dependent variable:
constant (at least one):
control:
number of groups:
number of trials per group: