Scientific Inquiry, Laboratory Safety, and Data Analysis
What you must know
Scientific method: hypothesis, prediction, independent and dependent variables, controlled variables, control group, repeats, and the distinction between accuracy, precision, reliability and validity. Sampling: random quadrats and transects, sample size and bias. Data handling: tables, mean, median, mode, range, percentage change, rates, ratios, uncertainty, significant figures, and choosing graph types (bar charts for discrete categories, line graphs and scatter graphs for continuous data). Conclusions: correlation is not causation, and anomalous results are noted before being excluded from calculations.
Laboratory safety: risk assessment before practical work, hazard symbols, personal protective equipment, safe use of Bunsen burners and glassware, heating and electrical safety, chemical storage and disposal, aseptic technique, safe handling of microorganisms, fume cupboards, and spill and accident procedures. Ethical approval is required for work with living organisms.
Traps and a worked example
Traps: labelling every controlled variable as 'the control group'; claiming repetition improves accuracy (it improves reliability); plotting line graphs for categorical data; dropping anomalies silently instead of reporting them.
Worked example: a measurement rises from 20 cm to 25 cm. Percentage change = (25 - 20) divided by 20, multiplied by 100 = +25 per cent. Rule of thumb: percentage change always divides by the original value, and the sign indicates direction - never divide by the new value.