P.06 Controls

Purpose of Controls

• Definition: A control is an experimental setup where the factor being tested (the independent variable) is absent or inactivated. This ensures any observed effect in the experiment is due to the independent variable alone.
• Importance:
  • Confirms that changes in the dependent variable are specifically caused by the independent variable.
  • Helps rule out the influence of other variables or unintended factors on the experiment’s outcome.

Example: Controls in the Rennin Experiment

1. Control Without Rennin:

• Set-Up:
  • Use a test tube with all the same contents as the experimental tubes but without rennin. Replace the enzyme with an equal volume of water to keep volumes consistent.
• Purpose:
  • Ensures that any observed milk clotting in the experimental tubes is due to the presence of rennin and not another factor in the setup.

1. Control With Boiled Rennin:

• Set-Up:
  • Use a test tube with rennin solution that has been boiled to denature the enzyme, rendering it inactive.
• Purpose:
  • Confirms that only active rennin can cause milk clotting. If clotting still occurs with boiled rennin, another factor might be influencing the outcome.

Setting Up Controls

• Consistency: All other conditions (e.g., temperature, pH, type of milk, sample volumes) must be identical between control and experimental setups.
• Inclusion of Water or Inactive Enzyme: In the absence of the active enzyme, replace it with water or a denatured enzyme to ensure volume consistency and eliminate confounding factors.

Summary of Controls in Experiments

Controls are essential in experimental design to verify that observed effects are due to the specific factor under investigation, helping to ensure the reliability and validity of results.