HSC Investigating Science cheat sheet

A hypothesis is a testable, falsifiable statement predicting the relationship between variables; it must be able to be proven wrong by data.

Independent variable: the factor deliberately changed by the investigator; dependent variable: the factor measured as a response; controlled variables: all other factors held constant.

Reliability is improved by repeating measurements and calculating a mean; validity is improved by controlling variables and using appropriate measurement techniques.

Accuracy refers to how close a measurement is to the true value; precision refers to how close repeated measurements are to each other.

Random error affects precision and can be reduced by averaging; systematic error affects accuracy and cannot be removed by averaging.

A controlled experiment includes a control group that receives no treatment or a placebo, allowing comparison against the experimental group.

Primary data are collected firsthand by the investigator; secondary data come from existing sources such as literature or databases.

A valid conclusion must be based on the evidence collected, address the hypothesis directly, and acknowledge limitations or sources of error.

The electromagnetic spectrum orders radiation by increasing frequency and decreasing wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.

Spectroscopy identifies substances by the unique pattern of wavelengths absorbed or emitted by their atoms; each element has a distinct spectral signature.

A telescope's resolving power improves with larger aperture diameter; the Rayleigh criterion gives resolution limit θ = 1.22 λ / D.

Digital sensors convert light intensity into electrical signals using pixels; higher pixel count increases spatial resolution but not necessarily sensitivity.

Radio telescopes detect long-wavelength radiation and can observe through dust clouds that block visible light; interferometry combines signals from multiple dishes to improve resolution.

Adaptive optics use deformable mirrors to correct for atmospheric distortion in real time, improving ground-based image sharpness.

The Doppler effect shifts observed wavelengths when a source moves relative to the observer; redshift indicates motion away and blueshift indicates motion toward.

Technological advances often depend on prior scientific discoveries, and new technologies in turn enable new scientific observations, creating a feedback cycle.

Anecdotal evidence is based on personal accounts and is not reliable for establishing cause and effect because it lacks controls and representative sampling.

Correlation does not imply causation; a third variable or coincidence may explain an observed association.

Confirmation bias is the tendency to seek and interpret evidence that supports existing beliefs while ignoring contradictory evidence.

A scientific claim is strengthened by independent replication, peer review, and convergence of evidence from multiple lines of inquiry.

Logical fallacies include ad hominem (attacking the person), straw man (misrepresenting an argument), and false dichotomy (presenting only two options).

Sample size and selection method affect the generalisability of findings; small or biased samples produce unreliable conclusions.

The placebo effect is a real physiological or psychological response to a treatment that is not due to the active ingredient; blinding reduces its influence.

Extraordinary claims require extraordinary evidence; the burden of proof lies with the person making the claim, not with the sceptic.

Peer review is a quality-control process in which independent experts evaluate a manuscript's methods, analysis, and conclusions before publication.

The precautionary principle states that when an activity raises threats of serious harm, precautionary measures should be taken even if some cause-and-effect relationships are not fully established.

Science informs policy but policy decisions also involve ethical, economic, and social values; scientific evidence is one input among many.

Ethical research requires informed consent, minimisation of harm, confidentiality, and approval by an ethics committee.

Conflicts of interest, such as industry funding of research, can bias study design, analysis, and reporting; disclosure and independent oversight mitigate this.

Public trust in science depends on transparency, reproducibility, and honest communication of uncertainty and limitations.

Risk assessment combines the probability of an event with the severity of its consequences; risk communication must convey both factors clearly.

Indigenous and local knowledge systems can provide valuable observations and context for scientific investigations when appropriately acknowledged and integrated.