MBBS Social and Preventive Medicine Flashcards

24 sample cards from the Social and Preventive Medicine deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Define the three measures of central tendency.

   Mean = arithmetic average $\bar{x} = \frac{\sum x}{n}$; Median = the middle value when data are arranged in order; Mode = the most frequently occurring value.

2. Give the formula for the sample standard deviation.

   $$s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n - 1}}$$ It measures the dispersion/spread of data around the mean; its square is the variance.

3. Define the coefficient of variation (CV) and its use.

   $$CV = \frac{s}{\bar{x}} \times 100$$ It is a unitless relative measure of dispersion used to compare variability between data sets with different units or widely different means.

4. Describe the properties of a normal (Gaussian) distribution.

   Bell-shaped and symmetrical about the mean; mean = median = mode. About 68% of observations lie within $\bar{x} \pm 1s$, 95% within $\bar{x} \pm 1.96s$, and 99.7% within $\bar{x} \pm 3s$.

5. Define probability and state its range.

   Probability is the likelihood of occurrence of an event. $$P(E) = \frac{\text{Number of favourable outcomes}}{\text{Total number of outcomes}}$$ Its value ranges from 0 (impossible) to 1 (certain); $0 \leq P(E) \leq 1$.

6. List the main types of probability (random) sampling.

   1) Simple random sampling, 2) Systematic sampling, 3) Stratified random sampling, 4) Cluster sampling, and 5) Multistage sampling. All give every unit a known, non-zero chance of selection.

7. Differentiate probability and non-probability sampling.

   Probability sampling: every unit has a known non-zero chance of selection; allows generalization and estimation of sampling error (e.g., simple random, stratified). Non-probability sampling: selection is subjective with unknown probability (e.g., convenience, quota, purposive, snowball); prone to bias.

8. What is the standard error of the mean (SEM) and its formula?

   SEM estimates how much the sample mean varies from the true population mean. $$SEM = \frac{s}{\sqrt{n}}$$ It decreases as sample size increases.

9. Define null hypothesis ($H_0$) and alternative hypothesis ($H_1$).

   $H_0$ states there is no difference/no association between groups (the assumption to be tested). $H_1$ states there is a real difference/association. Statistical testing aims to reject or fail to reject $H_0$.

10. Differentiate Type I and Type II errors.

    Type I error ($\alpha$) = rejecting a true null hypothesis (false positive). Type II error ($\beta$) = failing to reject a false null hypothesis (false negative). Power of a test = $1 - \beta$.

11. What is a p-value and the conventional level of significance?

    The p-value is the probability of obtaining the observed result (or more extreme) if the null hypothesis is true. By convention, $p < 0.05$ is considered statistically significant, leading to rejection of $H_0$.

12. Match common statistical tests to their use: t-test, chi-square, ANOVA, correlation.

    Student's t-test: compares means of two groups (quantitative). Chi-square ($\chi^2$): tests association between two categorical variables. ANOVA: compares means of three or more groups. Correlation (Pearson's $r$): measures strength/direction of linear association between two quantitative variables.

13. Name common software used for epidemiological data analysis.

    Epi Info (CDC/WHO, free, for outbreak analysis), SPSS, STATA, SAS, R, and Microsoft Excel. Epi Info is widely used for field epidemiology and outbreak investigations.

14. Define disease surveillance and name its two main types.

    Surveillance is the continuous, systematic collection, analysis and interpretation of health data, with timely dissemination for public health action. Types: 1) Active surveillance (health workers actively seek cases) and 2) Passive surveillance (routine reporting by facilities).

15. What is sentinel surveillance?

    A type of surveillance where selected reporting sites (sentinel sites/health facilities) provide high-quality data on specific conditions to monitor trends, used when comprehensive reporting is not feasible (e.g., influenza, HIV sentinel sites).

16. List components of a Health Information System (HIS).

    Data sources include census, vital statistics (births/deaths registration), notification of diseases, hospital/health facility records, epidemiological surveillance, disease registers, environmental health data, and health surveys. HIS supports planning, monitoring and evaluation.

17. What is the difference between Crude Death Rate and Infant Mortality Rate (with formulas)?

    $$\text{CDR} = \frac{\text{Total deaths in a year}}{\text{Mid-year population}} \times 1000$$ $$\text{IMR} = \frac{\text{Deaths under 1 year in a year}}{\text{Live births in same year}} \times 1000$$ IMR is a sensitive indicator of a community's overall health and socioeconomic status.

18. Define DALY and its two components.

    DALY (Disability-Adjusted Life Year) is a composite measure of disease burden: one DALY = one lost year of healthy life. $$\text{DALY} = YLL + YLD$$ where YLL = Years of Life Lost due to premature death and YLD = Years Lost due to Disability.

19. Name the main constructs of the Health Belief Model.

    Perceived susceptibility, perceived severity, perceived benefits, perceived barriers, cues to action, and self-efficacy. It explains health behavior based on a person's beliefs about a disease and the value of action to reduce its threat.

20. List the stages of the Transtheoretical (Stages of Change) Model.

    1) Precontemplation, 2) Contemplation, 3) Preparation, 4) Action, 5) Maintenance (and sometimes Termination/Relapse). It describes the process by which people change health behaviors over time.

21. State the five action areas of health promotion in the Ottawa Charter (1986).

    1) Build healthy public policy, 2) Create supportive environments, 3) Strengthen community action, 4) Develop personal skills, and 5) Reorient health services toward prevention and promotion.

22. Differentiate health education from health promotion.

    Health education is the process of providing information and skills to influence knowledge, attitudes and behavior for health (one component). Health promotion is broader, combining educational, environmental, political and organizational supports for actions conducive to health.

23. Compare individual, group, and mass approaches in health education methods.

    Individual approach: personal contact/counselling (most effective, two-way, but limited reach). Group approach: lectures, demonstrations, group discussions, role play (moderate reach, allows interaction). Mass approach: TV, radio, posters, newspapers (widest reach but least personal, one-way).

24. Define community participation and empowerment in public health.

    Community participation is the active involvement of the community in planning, implementing, and evaluating health programs (a PHC principle). Empowerment is the process by which communities gain control over decisions and resources affecting their health, enhancing self-reliance and ownership.

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