Processes of Science
Core concepts
Science is a way of testing ideas against evidence, not a body of fixed facts. Know the vocabulary of experimental design: hypothesis (a testable prediction), independent variable (what the experimenter changes), dependent variable (what is measured), controlled variables (everything held constant), and control group (a baseline with no treatment). Understand the difference between a hypothesis, a theory (a well-supported explanation), and a law (a statement of a consistent pattern). Be able to distinguish observation from inference, and qualitative from quantitative data.
Traps to watch
- Confusing correlation with causation; a trend in data does not prove mechanism.
- Calling a large sample "random" when it is only convenient.
- Forgetting that a control group must differ from the experimental group in only one factor.
- Reporting a mean without spread; a single trial is not evidence.
- Treating a measurement as exact; every instrument has uncertainty.
Worked example
A student tests whether fertilizer affects plant height. Fertilizer amount is the independent variable; height is the dependent variable; light, water, soil, and pot size are controlled. Ten plants per group reduce the effect of chance. If the fertilized group averages 18 cm and the control averages 12 cm, the student can say the fertilizer is associated with greater growth in this experiment, not that it "causes all plants to grow faster."
Rule of thumb
Change one variable, measure one variable, hold everything else constant, and repeat. If you cannot identify the variables and the control, you cannot evaluate the claim.