AP Biology FRQ: Experimental Design and Data Analysis
AP Biology FRQs test three core competency types: experimental design, data analysis, and conceptual application (including evolution, genetics, and physiology). Experimental design questions ask students to design a controlled experiment to test a specific hypothesis. A complete experimental design response contains: (1) Hypothesis — if-then form: 'If [independent variable is manipulated], then [dependent variable will change in a specific direction] because [mechanism].' (2) Independent variable (IV) — the one factor deliberately changed. (3) Dependent variable (DV) — what is measured. (4) Control variables — list all factors held constant to ensure validity. (5) Experimental group vs. control group — the control group receives no treatment or a standard treatment. (6) Replication — state the number of trials or organisms per group (minimum 3 for statistical validity). (7) Predicted results — describe what the graph or data would look like if the hypothesis is supported. AP Biology FRQ rubrics require the hypothesis to include a mechanism explanation — not just a directional prediction. 'Plants in high CO₂ will grow taller because increased CO₂ availability enhances the Calvin cycle's production of glucose, providing more substrate for cellular respiration and biosynthesis' earns mechanism credit. 'Plants in high CO₂ will grow taller' does not. Data analysis questions require reading the graph accurately, identifying trends, comparing groups, calculating rates if required, and drawing conclusions limited to what the data shows. Always state the direction and magnitude of the trend: 'Group A's cell count increased by 40% over 48 hours, while Group B's cell count remained stable, suggesting that...'