How population health and ethics is examined
Population health and ethics is 12.5% of the AMC MCQ blueprint, about 19 of 150 questions, and ethical issues also appear inside clinical questions in every area. Expect calculations, program details, public health actions and judgement questions where several answers are partly right.
Statistics you must be able to calculate
Draw the same 2 by 2 table every time: test result across the top, disease down the side.
| Measure | Formula | Meaning |
|---|---|---|
| Sensitivity | TP / (TP + FN) | Proportion of people with the disease who test positive |
| Specificity | TN / (TN + FP) | Proportion of people without the disease who test negative |
| Positive predictive value | TP / (TP + FP) | Chance a positive result is a true positive; rises with prevalence |
| Negative predictive value | TN / (TN + FN) | Chance a negative result is a true negative |
| Relative risk | Risk in exposed / risk in unexposed | Used in cohort studies and trials |
| Odds ratio | (a x d) / (b x c) | Used in case-control studies |
| Absolute risk reduction | Control event rate minus treatment event rate | The real-world difference a treatment makes |
| Number needed to treat | 1 / ARR | How many people to treat to prevent one event |
Worked example: if a statin lowers 5-year heart attack risk from 4% to 3%, the ARR is 1%, so the NNT is 1 / 0.01 = 100 people treated for 5 years to prevent one heart attack. The relative risk reduction is 25%, which sounds bigger: exam questions often test whether you notice the difference.
Study design and bias
| Design | Best for | Main weakness |
|---|---|---|
| Randomised controlled trial | Testing treatments | Cost, generalisability |
| Cohort study | Incidence and risk factors | Loss to follow-up, time |
| Case-control study | Rare diseases | Recall bias |
| Cross-sectional study | Prevalence | Cannot show cause and effect |
| Systematic review and meta-analysis | Pooling evidence | Only as good as the included studies |
- Confounding: a third factor linked to both exposure and outcome; reduce with randomisation, matching or adjustment.
- Selection bias, recall bias, lead-time bias, length-time bias: know one example of each.
Australian screening and prevention
| Program | Who | Interval |
|---|---|---|
| Cervical (HPV test) | Ages 25 to 74 | Every 5 years |
| Bowel (iFOBT) | Ages 45 to 74 | Every 2 years |
| Breast (mammogram) | Women 50 to 74 invited | Every 2 years |
| Lung (low-dose CT) | Ages 50 to 70 with significant smoking history | Every 2 years if low risk |
Also know absolute CVD risk assessment, AUSDRISK for diabetes, the RACGP Red Book and the principles of a good screening program. Full details are in our screening guide.
Communicable disease control and immunisation
- Notifiable diseases such as measles, tuberculosis, meningococcal disease, pertussis and many STIs must be reported to the public health unit; urgent ones by phone.
- Contact tracing identifies and manages exposed people, for example offering MMR or immunoglobulin after measles exposure.
- Outbreak investigation: confirm the outbreak, define cases, describe by time, place and person, form and test a hypothesis, control, communicate.
- Adult immunisation: influenza yearly for many groups, pneumococcal and shingles vaccines for older adults, pertussis in each pregnancy.
- Travel and refugee health: pre-travel advice and vaccines; screening new arrivals for TB, hepatitis B, strongyloides and other conditions.
Aboriginal and Torres Strait Islander health
Expect questions on asking the identification question, the 715 health assessment, earlier thresholds (such as CVD risk from 30), rheumatic heart disease, otitis media, Closing the Gap programs and the role of Aboriginal Community Controlled Health Organisations. See our First Nations health guide and our cultural safety guide.
The Australian health system
- Medicare provides rebates for MBS services and free public hospital care; the PBS subsidises medicines.
- Private health insurance covers private hospital care and extras.
- The NDIS funds supports for people with permanent and significant disability.
- Rural and remote areas face workforce shortages, distance and higher disease burden; the Royal Flying Doctor Service and telehealth help bridge gaps.
See Medicare and the MBS for IMGs and the PBS guide.
Ethics, consent and confidentiality
| Issue | Australian position |
|---|---|
| Informed consent | Disclose material risks (Rogers v Whitaker), alternatives and the option of no treatment |
| Refusal of treatment | A competent adult can refuse any treatment, even life-saving treatment |
| Mature minors | A young person who understands the treatment and its consequences can consent (Gillick principle) |
| Confidentiality | Can be breached when required by law or to prevent serious harm to the patient or others |
| Mandatory reporting | Child abuse in every state and territory; notification to Ahpra about impaired or unsafe practitioners |
| Open disclosure | Acknowledge, apologise, explain and support after adverse events |
More detail is in our guide to medical ethics in Australia.
Incidence, prevalence and likelihood ratios
- Incidence is the number of new cases in a period divided by the population at risk.
- Prevalence is the proportion of people who have the condition at a point in time. Prevalence is roughly incidence multiplied by average duration, so a treatment that keeps people alive longer can increase prevalence.
- Positive likelihood ratio = sensitivity / (1 minus specificity). A value above 10 strongly rules a condition in.
- Negative likelihood ratio = (1 minus sensitivity) / specificity. A value below 0.1 strongly rules a condition out.
Worked statistics example
A new test is used on 1,000 people, 100 of whom have the disease. It is positive in 90 of those with the disease and in 45 of those without.
| Disease present | Disease absent | Total | |
|---|---|---|---|
| Test positive | 90 (TP) | 45 (FP) | 135 |
| Test negative | 10 (FN) | 855 (TN) | 865 |
| Total | 100 | 900 | 1,000 |
- Sensitivity = 90 / 100 = 90%.
- Specificity = 855 / 900 = 95%.
- Positive predictive value = 90 / 135 = 67%.
- Negative predictive value = 855 / 865 = 98.8%.
If the same test is used where only 1% of people have the disease, the sensitivity and specificity stay the same but the positive predictive value falls sharply, because false positives outnumber true positives.
Health promotion and prevention
The Ottawa Charter for Health Promotion sets out five action areas that exam questions often ask you to match to an example:
| Action area | Example |
|---|---|
| Build healthy public policy | Tobacco taxes, plain packaging, sugar labelling |
| Create supportive environments | Smoke-free public places, safe cycling routes |
| Strengthen community action | Community-led programs designed with local people |
| Develop personal skills | Education on healthy eating or safe drinking |
| Reorient health services | Shifting focus from treatment to prevention |
Prevention is described as primary (preventing disease, such as immunisation), secondary (early detection, such as screening) and tertiary (reducing complications, such as cardiac rehabilitation).
Occupational health, driving and fitness to work
- Assess work-related injury and illness, and know that workers compensation schemes differ between states.
- Fitness to drive is assessed against the Austroads Assessing Fitness to Drive standards; patients have a duty to tell their licensing authority about conditions that affect driving, and doctors should advise them of it.
- Common exam conditions affecting driving: seizures, syncope, sleep apnoea, poor vision, dementia and diabetes with hypoglycaemia.
- Occupational exposures to know: asbestos (mesothelioma), silica (silicosis, a growing problem with engineered stone, now banned in Australia), noise and needlestick injury.
Worked examples
Worked example 1 · Treatment benefit
In a trial, 10% of patients on placebo and 6% on a new drug have a stroke over 3 years. How many patients need to be treated for 3 years to prevent one stroke?
- A 4
- B 10
- C 25
- D 40
- E 60
Show the reasoning
Answer C. The absolute risk reduction is 10% minus 6% = 4%, or 0.04. The number needed to treat is 1 / 0.04 = 25. The relative risk reduction is 40%, which is a common distractor.
Worked example 2 · Confidentiality
A 16-year-old asks for the oral contraceptive pill and asks that her parents not be told. She understands the risks and benefits. What is the most appropriate action?
- A Refuse until a parent consents
- B Prescribe and maintain confidentiality, with safety and STI advice
- C Call her parents for permission
- D Refer her to a gynaecologist
- E Prescribe only condoms
Show the reasoning
Answer B. A young person who understands the treatment and its consequences can consent under the mature minor principle. Confidentiality should be kept unless there is a risk of serious harm, such as abuse, which you should screen for. Encourage parental involvement but do not require it.
Common population health traps
- Reporting relative risk reduction when the question asks for absolute benefit.
- Assuming sensitivity changes with prevalence (it does not; predictive values do).
- Using a screening test on a patient with symptoms.
- Breaching confidentiality without a legal basis or serious risk.
- Forgetting that a 15-year-old may consent to treatment independently.
Free sample population health and ethics questions
Questions from our AMC MCQ bank. Choose your answer, then open the explanation.
A study compares mortality among 8000 long-term employees of a Victorian manufacturing plant with the general Victorian population. The standardised mortality ratio for all causes among the workers is 0.78, despite their exposure to industrial solvents. What is the most likely explanation for the lower mortality?
- ALead-time bias from health checks
- BRandom error from small numbers
- CProtective effect of solvents
- DRecall bias among the workers
- EHealthy worker effect
Show answer and explanation
Answer E. The healthy worker effect is a selection bias in occupational studies: the employed population excludes people too sick or disabled to work, so comparison with the general population makes workers look healthier. It can mask true occupational hazards. Using an internal comparison group, such as workers with lower exposure in the same industry, reduces this bias.
Learning point: Comparing workers with the general population underestimates occupational risk because of the healthy worker effect.
A systematic review of a complementary therapy for chronic pain includes 24 trials. The funnel plot shows that small trials with large beneficial effects are present, but there are almost no small trials showing no effect or harm; large trials cluster near no effect. What is the most likely explanation for this pattern?
- ALow statistical heterogeneity across trials
- BInadequate intention-to-treat analysis in large trials
- CTrue effect is larger in small populations
- DPublication bias against small negative trials
- ERandom sampling error in the large trials
Show answer and explanation
Answer D. A funnel plot graphs each study's effect size against its precision (or sample size). Without bias, smaller studies scatter widely and symmetrically around the pooled estimate. Asymmetry with a missing corner of small null or negative studies suggests publication bias (or other small-study effects such as poorer methodological quality), which will exaggerate the pooled benefit.
Learning point: Funnel plot asymmetry with missing small negative studies suggests publication bias or small-study effects.
The mother of a 10-year-old girl asks her GP how active her daughter should be. The girl plays netball once a week and spends about four hours a day on recreational screen time after school and on weekends. She is in the healthy weight range. According to Australian 24-hour movement guidelines for children aged 5-17, what is the recommendation?
- AFour hours of screen time is acceptable
- B30 minutes of activity on most days
- C60 minutes of MVPA every day
- D150 minutes of activity each week
- EOrganised sport once a week is enough
Show answer and explanation
Answer C. Australia's 24-hour movement guidelines for children and young people aged 5-17 recommend at least 60 minutes of moderate to vigorous physical activity daily, vigorous and muscle-strengthening activity on at least three days a week, no more than two hours of recreational screen time per day, and adequate sleep. Her screen time also needs addressing.
Learning point: Children aged 5-17 need at least 60 minutes of moderate to vigorous activity every day.
Practise more population health and ethics questions free
Every population health and ethics subtopic in our bank
The bank holds 375 population health and ethics questions across 62 subtopics. You can filter by any of them, build a custom block and track your accuracy subtopic by subtopic.
- 715 health assessment6
- Aboriginal Community Controlled Health Services6
- Absolute cardiovascular risk assessment7
- Absolute risk reduction6
- Adult National Immunisation Program8
- Aged care and My Aged Care6
- Alcohol guidelines7
- Bias and confounding6
- Capacity assessment6
- Chronic disease burden6
- Closing the Gap6
- Confidentiality and its exceptions6
- Conflicts of interest5
- Contact tracing8
- Cultural safety6
- Disability and the NDIS6
- End-of-life decisions and voluntary assisted dying5
- Good Medical Practice code5
- Health promotion models7
- Health workforce6
- Incidence and prevalence6
- Informed consent6
- Interpreters and communication5
- Jehovah's Witness and blood products5
- Lead-time and length-time bias5
- Levels of evidence and critical appraisal6
- Likelihood ratios6
- Mandatory notification of practitioners5
- Medical errors and incident reporting5
- Medicare and PBS7
- Minors and Gillick competence6
- National screening programs8
- Notifiable diseases and public health units7
- Number needed to treat and harm6
- Occupational health and workplace injury7
- Odds ratio6
- Open disclosure5
- Otitis media and hearing in Aboriginal children6
- Outbreak investigation7
- P-values and confidence intervals6
- Physical activity and obesity prevention7
- Positive and negative predictive value6
- Privacy and medical records5
- Private vs public health system6
- Professional boundaries5
- RACGP Red Book preventive activities7
- Refugee and migrant health screening7
- Refusal of treatment5
- Relative risk6
- Research ethics5
- Rheumatic heart disease and acute rheumatic fever7
- Rural and remote practice6
- Screening test evaluation6
- Sensitivity and specificity6
- Smoking cessation and vaping7
- Social determinants of health6
- Study designs6
- Substitute decision-makers and advance care directives5
- Survival curves5
- Telehealth5
- Travel medicine7
- Type I and II errors and power6
Common questions
How many population health questions are in the AMC MCQ?
Population health and ethics is 12.5% of the blueprint, about 19 of 150 questions, and ethics also appears inside clinical questions.
Which statistics formulas do I need for the AMC MCQ?
Sensitivity, specificity, predictive values, relative risk, odds ratio, absolute risk reduction and number needed to treat.
Does prevalence change sensitivity?
No. Sensitivity and specificity are properties of the test. Prevalence changes the positive and negative predictive values.
What is Gillick competence?
The principle that a young person under 18 who understands the nature and consequences of a treatment can consent to it.
Sources
Clinical content is summarised from current Australian guidance at the date above. Guidelines change, so always check the latest edition.