Question

The only variables in the lab procedure are the independent variable,
and the dependent variable,

Hypothesis:If plants grow in soil containing worms, then the plant growth will be greater, because worms help decompose organic matter and distribute it through the soil in a form that plants can use.

Notice that the only two factors that change during the experiment are the variables of the hypothesis, underlined above. All other factors are held constant.

Answer 1

Fill in the blanks like this:

The only variables in the lab procedure are the independent variable, the presence of worms in the soil, and the dependent variable, the plant growth (for example: plant height, biomass, or number of leaves).

Notes and suggestions
- Operationalize the dependent variable: decide how you will measure “plant growth” (e.g., height in cm measured weekly, final dry mass in g, or leaf count).
- Define the independent variable precisely (e.g., worms present vs. absent, or specific worm density such as 5 worms per pot).
- Keep other factors constant: same plant species and age, same soil type and volume, identical pot size, same light and temperature, same watering schedule, same fertilizer (if any), same planting depth, and equal replication and randomization.
- Include a control group (no worms) so you can compare.

This ensures the only factors that change are the independent variable (worms) and the dependent variable (plant growth).