Variables and Experiment Design

Variables in Experiments

• A variable is something that can change in an experiment
• The three types of variables are dependent, independent, and control
• The independent variable is the one that scientists change
• The dependent variable is the one that scientists measure
• Control variables are kept the same to isolate the effect of the independent variable

Experiment Design

• Scientists only change one thing at a time to see its effect on the dependent variable
• Control variables are important for accurate results

Hypothesis

• A hypothesis is a prediction about what will happen in an experiment
• It is an explanation, often supported by previous knowledge

Risk Assessment

• A risk assessment needs a hazard, risk, and safety precaution
• A hazard is something that has the potential to cause harm or damage
• A risk is how that hazard could cause harm or damage
• A safety precaution is what to do to avoid the risk

Measurements and Observations

• A measurement is the result of an experiment that can be quantified using scientific equipment
• Examples include mass, distance, time, force, wavelength, and temperature
• An observation is something that can be seen in an experiment, like colour changes, light emission, or movement
• Examples include colour, giving off light, gas production, etc

Types of Data

• Continuous data has numerical values that can be any size (e.g., mass)
• Discrete data has numerical values that can be put into categories (e.g., eye colour)

Tables and Graphs

• Results tables organize experimental data with independent and dependent variables
• Independent variable on the left, Dependent variable on the right
• Graphs visually depict relationships between variables
• Bar charts suitable for discrete data; line graphs for continuous data
• Graphs should have clear titles and labels, appropriate scales, and lines of best fit where needed

Graphing Considerations

• Independent variable on the x-axis; dependent on the y-axis
• Scales should be easy to understand and evenly spaced (e.g., use 1, 2, 5, 10 etc.)