Example experiment topic: Which fertilizer works the best?
Question: How does the type of fertilizer affect the growth of a plant?
Hypothesis: Plants that are given xxx brand fertilizer will grow taller than plants given yyy or zzz brand fertilizers.
Independent variable (the thing YOU change) - type of fertilizer
Constants - plant type, amount of water each day, amount of sunlight each day, same soil/conditions, and anything else you might do over the course of your experiment. These conditions must stay the same for each plant (or trial in other experiments)
Control - the one plant that you don't give any fertilizer to, but all the other conditions are the same
Dependent variable (the thing you MEASURE) - the growth of the plant
