Data analysis and limitations

Parallel case (model only, not today's prompt): a different team tested how caffeine concentration affects the heart rate of Daphnia (water fleas) under a microscope.\n\nClaim: Increasing caffeine concentration raises Daphnia heart rate, showing a dose-response relationship.\n\nEvidence: In the 0 mg/L control, the average heart rate was 180 beats per minute. At 20 mg/L caffeine the average rose to 240 beats per minute, and the 10 mg/L group fell in between at about 210 beats per minute.\n\nReasoning: As the dose of caffeine rose, the biological effect (faster heartbeat) increased. This is what physiology predicts: caffeine is a stimulant that blocks the signals that normally slow the heart, so more caffeine drives more heartbeats per minute. The steady climb from control to 20 mg/L shows the effect scales with dose rather than jumping at random.\n\nLimitations:\n- Small sample size (only a few Daphnia per concentration) means one unusually fast or slow animal could shift the average a lot.\n- Heart rate was counted by eye while watching a fast, tiny heart, so the same beats could be tallied differently by different observers or on different trials.