Practical planning, analysis and evaluation

Learning objectives

• Design a justified biological investigation.
• Choose appropriate graphical and statistical comparisons.
• Evaluate specific uncertainty and bias.

The big idea

Planning begins with a testable question, operational definitions and a method that can produce valid comparisons. Select independent and dependent variables, suitable controls, independent replication and an appropriate range; ethical and safety constraints shape what can be investigated.

Graphing and statistical analysis should match the data and study design. Correlation does not establish causation, and statistical significance does not automatically imply a large biological effect. Improvements should target identified limitations, such as biased sampling or imprecise timing, rather than simply requesting more expensive apparatus.

Investigate and explain

Using the worked example as supplied data, predict the effect of changing one condition. Draw a labelled model, record your reasoning and identify a variable that would need controlling. No human, animal or microbial experiment is required.

No exact PhET model is claimed for this topic. Use diagrams and supplied-data reasoning instead.

Open the interactive investigation

Check your understanding