Statistics
What is incidence? What is prevalence?
Incidence refers to the number of new cases of a disease or condition that occur in a specific population during a defined period of time.
Prevalence refers to the total number of cases (both new and existing) of a disease or condition in a specific population at a given point in time.
What are 3 main features of this graph?
Title: expenditure ($ billion) on public and private hospitals, by source of funds, constant prices, 2012-2013 to 2021-2022.
Trends: state and territory spend the most on hospitals, state and federal government funding is steadily increasing, non-government spending has remained the same
other acceptable answers
Cohort study, case-control, cross sectional, RCT
tests a theory, shows prevalence, gives prognosis, identifies risk factors
RCT: Tests a theory by randomly assigning participants to intervention or control groups.
Cohort Study: Gives prognosis by following participants over time to observe the development of outcomes based on exposure.
Case-Control Study: Identifies risk factors by comparing those with a condition to those without and looking for differences in past exposures.
Cross-Sectional Survey: Shows prevalence by measuring the frequency of a condition or behavior in a population at a single point in time.
List 3 PRIMARY preventions used to reduce alcohol related harm
Primary prevention refers to actions taken to prevent a disease or injury before it occurs.
- increased taxation
- reduced outlet density
- raised minimum drinking age
List 4 ways to look after your health as a doctor
- regular exercise / sleep / eat well (self care)
- seek professional support when needed
- mindfulness and stress management
- self reflection
etc.
A test has a positive predictive value of 54% and a negative predictive value of 67%. What does this mean?
PPV: 54% of the people with positive test results are true positives, while the remaining 46% are false positives.
NPV: 67% of the people with negative test results are true negatives, while 33% are false negatives.
What is the X and Y axis on this graph?
X: financial year
Y: percent (%)
List these studies from most reliable to least reliable:
case series, case control, prospective cohort, randomised control trial, case report, cross sectional
1. Randomized Controlled Trial (RCT) – Considered the gold standard for testing causality because participants are randomly assigned to different groups, reducing bias.
2. Prospective Cohort Study – Follows a group of people over time to see how different exposures affect outcomes, offering strong evidence but without the randomisation of RCTs.
3. Case-Control Study – Compares people with a condition (cases) to those without it (controls), looking retrospectively to identify possible risk factors or exposures.
4. Cross-Sectional Study – Observes a specific population at one point in time to assess prevalence and associations, but it cannot establish causality.
5. Case Series – Describes characteristics of a group of patients with a certain condition but lacks control groups, making it less reliable for drawing broader conclusions.
6. Case Report – Describes a single patient's case, often useful for rare conditions but provides the least evidence due to its anecdotal nature and lack of generalizability.
If a person has a high absolute CVD risk, what is meant by this?
(definition of absolute CVD risk & what percentage range)
Absolute risk is the numerical probability of a cardiovascular disease event occurring within five years, expressed as a percentage.
For high risk, the patient’s risk is 10% or higher, meaning that 10 (or more) out of every 100 people like them are likely to have a CVD event within the next five years.
Describe 3 ways to improve health screening uptake amongst Aboriginal and Torres Strait Islander communities
- collaboration with community members
- ensure continuity of care
- flexibility with appointment times
- acceptable screening procedure/test
Relative Risk is defined as the ratio of the probability of an event occurring in the exposed group to the probability of the same event occurring in the unexposed group.
RR = risk (exposed) / risk (unexposed)
RR = risk (obese) / risk (not obese)
Risk (obese) = 60 / 60+40 = 0.6
Risk (not obese) = 15 / 15+75 = 0.1667
RR = 0.6 / 0.1667 = 3.6
The relative risk (RR) of approximately 3.60 indicates that obese individuals have about 3.6 times the risk of developing diabetes compared to those who are not obese.
What is the independent and dependent variable in this graph?
Independent: age group and gender
Dependent: prevalence of self-reported heart, stroke, and vascular disease
What study types are observational and analytical?
Cohort, case-control and cross-sectional
(show diagram)
Pre event: road conditions, visibility, speed limits etc.
Event: guard rails, recovery lanes, oncoming traffic
Post event: access to hospital, phone reception, witnessed crash
List 4 characteristics of an effective screening TEST
- highly sensitive
- highly specific
- relatively high PPV
- relatively high NPV
- validated, safe, acceptable
Define sensitivity and specificity. What is the formula for each? Calculate them from this data table
Sensitivity: the proportion of true disease cases correctly identified as positive (SNOUT - Sensitivity when Negative rules people OUT)
TP/TP+FN: 80/80+20 = 80%Specificity: the proportion of true non-disease cases that correctly identifies as negative (SPIN - Specificity when Positive rules people IN)
TN/TN+FP: 90/90+5 = 94.74%
List 3 modifiable risk factors that could have contributed to the decrease of CHD in this graph
- increased physical activity
- reduced cholesterol diet (trans/saturated fats)
- smoking cessation
- reduced alcohol intake
- control of hypertension
RCTs are a prospective, comparative and quantitative experiment under control conditions, using one assigned control group and one assigned treatment group.
- testing treatment efficacy
- establishing causality
Carcinogen: agent directly involved in the promotion of cancer
- tobacco smoke
- asbestos
- UV radiation
Mutagen: physical or chemical agent that results in increased frequency of mutations, potentially leading to cancer
- X rays
- benzene
- formaldehyde
Define epidemic, endemic and pandemic
Epidemic: unusual occurrence of a disease, exponential rise in number of cases and subsequent decline
Endemic: disease that occurs at consistently high levels in a population
Pandemic: epidemic that covers a wide geographic area and affects a large proportion of the worlds population
The odds ratio is defined as the ratio of the odds of an event occurring in the exposed group to the odds of the event occurring in the unexposed group.
OR = Odds (alcohol users) / Odds (non users)
Odds (alcohol users) = a / b = 50 / 150 = 0.333
Odds (non users) = c / d = 10 / 90 = 0.111
OR = 0.333 / 0.111 = 3
* Same as A x D / B x C (50 x 90 / 150 x 10) just a mathematical rearrangement
The odds ratio of 3 indicates that alcohol consumers have 3 times the odds of developing liver cirrhosis compared to non-consumers.
Name the groups that are statistically significant for consuming sugary drinks at least once during the week from this graph
- Family type
- socioeconomic status
Error bars indicate the uncertainty or variability in the data (such as a confidence interval). If the error bars between two groups do not overlap or only minimally overlap, it suggests a statistically significant difference between the groups.
What are 3 weaknesses of a prospective cohort study?
- time consuming / expensive (may need to follow participants for many years for disease development)
- loss to follow up (attrition bias due to lengthy nature of study)
- not suitable for rare diseases (would require extremely large sample sizes to do so)
List the 5 criteria for an effective population based screening PROGRAM
- Condition is an important health problem
- recognisable latent or early symptomatic stage
- natural history of condition is adequately understood
- suitable and acceptable test available
- accepted treatment for patients identified with condition
What is the Bradford Hill Criteria? List and describe 4 Bradford Hill Criteria
Principles used to determine whether a relationship between an exposure and an outcome is likely to be causal.
1. Strength of Association: A strong association (e.g., a high relative risk or odds ratio) between the exposure and the outcome increases the likelihood of a causal relationship. The stronger the association, the less likely it is due to chance.
2. Consistency: If the same association is repeatedly observed in different studies, populations, settings, and circumstances, it strengthens the case for causality.
3. Specificity: Causality is more likely if a specific exposure is associated with a specific disease or outcome, rather than multiple unrelated outcomes. However, this criterion has limited applicability in modern multifactorial diseases.
4. Temporality: The exposure must precede the outcome for a causal relationship. This is one of the most critical criteria, as causality cannot be inferred if the outcome occurs before the exposure.
5. Biological Gradient (Dose-Response Relationship): A causal relationship is more likely if increasing levels of exposure lead to an increased risk of the outcome. This indicates a gradient effect.
6. Plausibility: The association should make biological sense based on current scientific knowledge. If there is a reasonable biological mechanism to explain the association, it supports causality.
7. Coherence: The relationship between the exposure and the outcome should be coherent with what is already known about the disease's natural history and biology. The proposed causal relationship should not contradict existing knowledge.
8. Experiment: If an intervention or experiment (such as reducing the exposure) leads to a reduction in the incidence of the outcome, it provides strong evidence for causality.
9. Analogy: If a similar association has been observed with other exposures and outcomes, it may suggest that the current observed association could be causal as well. This criterion involves reasoning by analogy.