Biology • Year 12 • Module 8 • Lesson 15
Benefits of Epidemiological Studies
Lock in the vocabulary of epidemiological benefit, the benefit chain, the three risk measures and the screening criteria, the foundations for evaluating benefits using examples at HSC level.
1. Complete the benefit chain
An epidemiological study delivers its full benefit only when every link in the chain holds. Write the missing labels into boxes A–H using the lesson Key Terms and the card "From association to action". 8 marks
| Box | Your label |
|---|---|
| A | |
| B | |
| C | |
| D | |
| E | |
| F | |
| G | |
| H |
2. Term–definition match
The definitions below are shuffled. Write the matching term from this list in the right-hand column: risk factor, screening, public health, resource allocation, relative risk, attributable risk, sensitivity, specificity, lead-time bias, overdiagnosis. 10 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 2.1 | The proportion of people who genuinely have the disease that a test correctly flags as positive. | |
| 2.2 | Detecting disease that would never have caused symptoms during that person's lifetime, then counting the person as cured. | |
| 2.3 | A factor linked with a higher probability of developing a disease. | |
| 2.4 | An estimate of how many cases in a population would be prevented if a particular exposure were removed. | |
| 2.5 | Testing people who have no symptoms in order to detect disease or risk early. | |
| 2.6 | The apparent lengthening of survival caused purely by moving the diagnosis date earlier, without the person living any longer. | |
| 2.7 | Deciding where funding, staff and services are most needed. | |
| 2.8 | The proportion of people without the disease that a test correctly clears as negative. | |
| 2.9 | Organised actions that protect and improve the health of a whole population. | |
| 2.10 | How many times more likely disease is in the exposed group than in the unexposed group. |
3. True or false, with correction
Circle T or F. If the statement is false, write the corrected version on the line below. 8 marks (1 T/F + 1 correction where needed)
3.1 Finding that two variables are associated in an epidemiological study proves that one causes the other. T / F
3.2 An epidemiological study can benefit public health even though it treats no individual patient. T / F
3.3 A study becomes a benefit at the moment it is published. T / F
3.4 If incidence of a disease falls while prevalence rises, prevention must have failed. T / F
4. Function recall
Answer each question in 1–2 sentences using precise lesson terminology. 10 marks (2 each)
4.1 What is the function of attributable risk in a public-health spending decision?
4.2 What is the function of incidence data in health-service planning, and how does it differ from prevalence?
4.3 What is the function of reporting rates separately for remote and metropolitan populations?
4.4 What is the function of specificity in judging whether a screening test is acceptable?
4.5 What is the function of the final link in the benefit chain, the outcome check?
5. Build a concept map
Draw labelled arrows between the six terms below. Each arrow must carry a linking phrase (e.g. "identifies", "justifies", "measures", "limits"). Aim for at least 6 labelled arrows. 6 marks
Supplied terms: epidemiological study · risk factor · prevention campaign · screening program · resource allocation · equity of access.
6. Cloze, fill in the blanks
Complete the paragraph using words from the word bank below. Each word is used once. 10 marks
An epidemiological study examines patterns of disease and exposure across whole _______________. Its output is not a treatment but _______________ about how disease is distributed and which factors raise risk. Identifying a modifiable _______________ allows the health system to act through _______________ before people become ill, or through a _______________ program that detects disease early in people without symptoms. Counts matter as well as risks: _______________ shows how fast new cases are arriving, while _______________ shows how many people need ongoing care right now. Because a small increase in risk applied to a very common exposure still produces many cases, _______________ risk is the measure that usually drives budgets. Finally, a benefit reaching only some groups is a partial benefit, so _______________ must be examined, and later data must check the _______________ rather than assuming the response worked.
Q1, Labelled benefit chain
A: finding (the study identifies a pattern or risk factor). B: decision (a campaign, screening program, regulation or policy). C: implementation (the response is delivered so the target population can reach it). D: outcome check (new data test whether exposure or disease rates actually moved). E: relative risk. F: absolute risk. G: attributable risk. H: awareness (if any link breaks, the benefit shrinks to awareness only).
Q2, Term–definition matches
2.1 sensitivity · 2.2 overdiagnosis · 2.3 risk factor · 2.4 attributable risk · 2.5 screening · 2.6 lead-time bias · 2.7 resource allocation · 2.8 specificity · 2.9 public health · 2.10 relative risk.
Q3, True / false with correction
3.1 False. Correction: an association is a starting point, not proof of causation. Health authorities act when the association is strong, consistent across studies and populations, shows the exposure clearly preceding the disease, and is biologically plausible, and when confounding and bias have been considered.
3.2 True.
3.3 False. Correction: publication alone produces awareness, not benefit. Evidence becomes a benefit only when it leads to a decision that is implemented and that the target population can actually access, and when later data check the outcome.
3.4 False. Correction: falling incidence with rising prevalence usually means treatment improved, so people live longer with the disease. Incidence is the measure that judges prevention, and a falling incidence indicates prevention is working even as the number of people needing ongoing care grows.
Q4, Function recall answers
4.1 Attributable risk: It estimates the share of cases in a population that would disappear if an exposure were removed, so it identifies the largest removable portion of a disease burden. This is why a modifiable exposure with only a modest relative risk, such as physical inactivity, can still be the highest prevention priority, while a large relative risk on a rare exposure may not be.
4.2 Incidence: Incidence counts new cases arising in a period, so it shows how fast fresh demand is arriving and whether prevention is working. Prevalence counts people living with the disease at one point in time, so it sizes the ongoing care the system must fund. The two can move in opposite directions, so a planner using only one can misread demand.
4.3 Disaggregated reporting: A national average hides which groups are missing out. Reporting rates separately by region, income or Indigenous status exposes both a higher disease burden and an access barrier, which is what allows an evaluation to judge whether a benefit is equitable rather than merely large on average.
4.4 Specificity: Specificity is the proportion of healthy people the test correctly clears, so it controls the false-positive rate. Low specificity means large numbers of well people receive positive results, carrying anxiety, follow-up procedures and cost despite never having been ill, which can outweigh the benefit of the cases the test finds.
4.5 Outcome check: Later data test whether exposure, behaviour or disease rates actually changed after the response was implemented. Without it a benefit is asserted rather than evaluated, and the study cannot be said to have delivered more than awareness.
Q5, Sample concept map
Correct maps should include arrows such as:
- epidemiological study identifies a modifiable → risk factor
- risk factor justifies targeting it with a → prevention campaign
- risk factor identifies who should be offered a → screening program
- epidemiological study supplies incidence and prevalence data that guide → resource allocation
- equity of access limits the real benefit delivered by a → prevention campaign (or screening program)
- screening program generates data that feed back into a further → epidemiological study
Award 1 mark per correct labelled arrow (maximum 6). Do not award a mark for an arrow implying the study directly treats patients.
Q6, Cloze answers (in order)
populations · evidence · risk factor · prevention · screening · incidence · prevalence · attributable · equity · outcome