Investigative Skills – Experimental Design Essentials

Hypothesis

  • Statement predicting the relationship between variables
  • Must link independent and dependent variables

Aim

  • Format: “To see if … (independent variable) affects … (dependent variable).”

Variables

  • Independent Variable (IV): deliberately changed; input variable
    • State as a full description, e.g. “volume of water (mL)”
  • Dependent Variable (DV): measured outcome
    • Describe precisely, e.g. “temperature of water (°C)”
  • Fixed Variables (Controls): kept constant to ensure a fair test; specify how each is held constant

Method Requirements

  • Write in clear, logical point form
  • Design must directly address the aim
  • Use a range (≥3 distinct values) of the IV
  • Specify what is measured and how (instrument + unit)
  • Name appropriate equipment for every action (e.g. syringe for 5 mL5\,\text{mL} water, pipette for iodine drop)
  • Repetition & Reliability
    • Repeat each IV value ≥3 times
    • Average results to increase reliability
  • Control Setup (when applicable)
    • Identical to experiment except for the IV
    • Provides comparison, ensuring validity