Basic Principles of Science
Science as a process
Science is a way of testing ideas against evidence, not a fixed body of facts. A hypothesis is a testable, falsifiable prediction; a scientific theory is a broad, well-supported explanation (not a guess); a law describes a consistent relationship. Candidates should know experimental design: the independent variable is manipulated, the dependent variable is measured, and controlled variables are held constant. A control group provides a baseline, while replication, randomization, and adequate sample size reduce bias and chance error. Distinguish accuracy (closeness to the true value) from precision (repeatability). Measurement questions use SI units, unit conversions, significant figures, and percent error; data questions require choosing the right graph and reading axes carefully. Correlation does not establish causation, and confounding variables can create false associations.
Traps
Watch for “proves” (science supports or fails to reject), confusing a hypothesis with a prediction, calling controlled variables a control group, and treating precise but wrong data as accurate. Peer review and reproducibility matter.
Worked example
A student tests whether colored light affects bean growth. Independent variable: light color. Dependent variable: height or mass gained. Controlled: soil, water, temperature, bean type. Control group: white light or no filter. If repeated measurements cluster tightly but sit 2 cm from the true value, the data are precise but not accurate. Rule of thumb: change one variable at a time and include a comparison group.