Community Medicine (PSM) Practical – Worked Solutions

Covering all 9 papers/pages you've sent (Biostatistics, Epidemiology exercises, and Case-based scenarios). Answers follow standard 3rd-year MBBS PSM practical format (Park's Textbook of PSM conventions).

PAPER 1 – Biostatistics (Boys/Girls weight; Immobility duration)

Ex 1 – Boys (n=63, mean 36.8, SD 8.6) vs Girls (n=37, mean 34.2, SD 6.5)

a) Test: Unpaired (independent samples) Student's t-test – data are quantitative (continuous weight), two independent groups, comparing two means, sample size >30 with SDs known.

b) Null hypothesis: H₀: There is no significant difference between the mean weight of boys and mean weight of girls at 10 years of age (μ₁ = μ₂); any observed difference is due to chance.

c) Calculation: SE = √(8.6²/63 + 6.5²/37) = √(1.174 + 1.142) = √2.316 = 1.522 t = (36.8−34.2)/1.522 = 2.6/1.522 = 1.71 df = 63+37−2 = 98; table t (0.05, df≈98) ≈ 1.98 Since calculated t (1.71) < table t (1.98) → not significant. Fail to reject H₀ — no statistically significant difference in mean weight between boys and girls. (matches the 1.71 already marked)

Ex 2 – Immobility days (n=10): 7,9,9,11,11,12,13,16,17,19

Mean = 124/10 = 12.4
Median = (11+12)/2 = 11.5
Σ(x−mean)² = 134.4 → Sample variance = 134.4/9 = 14.93 → SD ≈ 3.86 (≈3.83 as marked, minor rounding)
CV = (SD/Mean)×100 = 3.86/12.4×100 ≈ 31.1% (≈30.8% as marked)

PAPER 2 – Case Scenario (Avantika / Sunil-Geeta-Yash / Postnatal woman)

Case 1 – Newborn with midline spinal defect (Meningomyelocele/Spina bifida – Neural Tube Defect)

a) Supplement to prevent this: Folic acid – 400 µg (0.4 mg)/day for all women of reproductive age periconceptionally (at least 1 month before conception through first trimester); for women with a previous NTD-affected pregnancy, higher dose of 4–5 mg/day is recommended.

b) National program applicable for the child: Rashtriya Bal Swasthya Karyakram (RBSK) – screens children 0–18 years for early detection and management of birth defects/disabilities.

c) Any 4 diseases/defects covered under RBSK (4 D's):

Neural tube defect / Cleft lip & palate (Defects at birth)
Vitamin A/D deficiency, Severe Acute Malnutrition (Deficiencies)
Rheumatic heart disease, otitis media (Diseases)
Vision/hearing impairment, autism/learning delay (Development delays & Disabilities)

Park's PSM, p. 578 (RBSK, 4 D's – defects at birth, diseases, deficiencies, developmental delays including disability)

Case 2 – Sunil, Geeta, Yash (growth monitoring)

a) SAM diagnostic criteria (6–59 months): Any ONE of:

Weight-for-Height/Length < −3 SD (WHO standards), OR
MUAC < 11.5 cm, OR
Bilateral pitting oedema of nutritional origin (regardless of anthropometry)

b) Which child has SAM and why:

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