Controlled Experiments and Hypothesis Testing

What is a Controlled Experiment?

A controlled experiment is a test where all factors (variables) are kept constant except one.
It's designed to test a scientific hypothesis.

To determine if a hypothesis is correct.
Allows for testing the effect of one variable, ensuring all other conditions are the same.

Objective: Test if a fertilizer makes plants grow bigger, lusher, and produce more.
Steps to Set Up:
- Select two plants of the same species (Plant A and Plant B) with identical size, health, and age.
- Use identical pots and the same type and amount of soil for both plants.
- Water both plants equally and place them in the same location to ensure equal sunlight and temperature exposure.
Variable Control:
- Everything kept the same except for the application of fertilizer.
- Plant A receives fertilizer; Plant B does not.

Hypothesis: Plant A (with fertilizer) will grow bigger than Plant B (without fertilizer).
Data Collection:
- Regularly measure both plants over a set period (e.g., weekly for 3 months).
- Record these measurements as data.

Compare growth measurements of Plant A and Plant B at the end of the experiment.
If Plant A grows bigger than Plant B, the results support the hypothesis.

Test: Effectiveness of fertilizer on plant growth.
Hypothesis: Fertilizer will make the plant grow bigger.
Measurements: Growth of both plants.
Result Evaluation: Hypothesis is supported if the fertilized plant (Plant A) grows larger than the non-fertilized plant (Plant B).

Independent Variable: Fertilizer (what is changed/controlled by the experimenter).
Dependent Variable: Plant growth (what is measured and expected to change in response to the independent variable).

Further details on independent and dependent variables will be covered in another session.