MNJ11-001
(May 2013):

MNJ-P-OSCE 11. Clinical biostatistics_page_4_Figure_8.jpeg

  1. What is the name of this plot?
  2. What is the arrowed figure at the bottom named as?
  3. In the given studies, which individual study showed the best association in view of the outcome?
  4. Where is this plot primarily used in medical research?

Answer

  1. Name: Forest plot (Blobbogram).
  2. Arrowed figure: Diamond (representing the pooled/summary effect estimate; the width of the diamond represents the 95% confidence interval).
  3. Best association: Study by Kalyan (shows greatest effect size / precision).
  4. Usage: Systematic reviews and Meta-analyses.

MNJ11-002
You are doing a clinical trial: "Is acupuncture better for depression than medication?". The results are shown below:

Treatment Group Improvement (+) No Improvement (−) Total (N)
Acupuncture 12 15 27
Medication 6 14 20
  1. Calculate the Odds Ratio (OR).
  2. What is the significance / interpretation of the calculated Odds Ratio?

Answer

  1. Odds Ratio Calculation:
    Odds in Acupuncture group=ab=1215=0.80
    Odds in Medication group=cd=614=0.428
    Odds Ratio (OR)=a×db×c=12×1415×6=16890≈1.87

  2. Interpretation:
    The odds of clinical improvement in depression are approximately 1.87 times (nearly double) higher in the acupuncture group compared to the standard medication group.


MNJ11-003
In an area, the Under-5 Mortality Rate (U5MR) is 8 per 1000 live births.

  1. Calculate the Child Survival Index (CSI) in that area and write down the formula.
  2. Write down the formulas for Incidence, Period Prevalence, and Stillbirth Rate.
  3. Write down the formulas for Case Fatality Rate (CFR), Attack Rate, and Secondary Attack Rate (SAR).

Answer

  1. Child Survival Index (CSI):
    Child Survival Index=1000−Under-5 Mortality Rate10=1000−810=99210=99.2%

  2. Epidemiological Formulas:

    • Incidence:
      Incidence=Number of new cases of disease during a specified periodTotal population at risk during the same period×1000
    • Prevalence:
      Prevalence=Number of existing (old + new) cases at a given point/periodTotal estimated population at that time×100
    • Stillbirth Rate:
      Stillbirth Rate=Fetal deaths ≥28 weeks gestation / birthweight ≥1000 gTotal births (live births + stillbirths)×1000
  3. Attack and Fatality Rates:

    • Case Fatality Rate (CFR):
      CFR=Total deaths due to a specific diseaseTotal diagnosed cases of that disease×100
    • Attack Rate:
      Attack Rate=Number of new cases during an epidemic/outbreakTotal susceptible population at risk×100
    • Secondary Attack Rate (SAR):
      SAR=Number of secondary cases among contacts within incubation periodTotal susceptible contacts exposed to primary case×100

MNJ11-004

MNJ-P-OSCE 11. Clinical biostatistics_page_5_Picture_7.jpeg

  1. What is the name of this plot?
  2. What is its use in medical research?
  3. Describe the following designated points in this plot:
    • Point A
    • Point B
    • Point B1

Answer

  1. Name: Box-and-Whisker Plot (Box Plot).
  2. Use: Displays a 5-number statistical summary of a continuous numerical variable (minimum, 25th percentile, median, 75th percentile, maximum, and potential outliers/skewness).
  3. Components:
    • Point A: Median (50th percentile / second quartile Q2).
    • Point B: Lower quartile (25th percentile / first quartile Q1).
    • Point B1: Upper quartile (75th percentile / third quartile Q3).
    • (The interquartile range IQR=Q3−Q1 forms the central box).

MNJ11-005
The following 2x2 table demonstrates the relationship between cigarette smoking and lung cancer:

Cigarette Smoking Developed Cancer Did Not Develop Cancer Total
Yes 70 6930 7000
No 2 2998 3000
  1. Calculate the Relative Risk (RR).
  2. What is the clinical interpretation and value of Relative Risk in medical research?

Answer

  1. Relative Risk (RR) Calculation:

    • Incidence in exposed (Smokers)=707000=0.010=10 per 1000
    • Incidence in non-exposed (Non-smokers)=23000≈0.00067=0.67 per 1000 (or 11000 rounded)
    • Relative Risk (RR)=Incidence in exposedIncidence in non-exposed=70/70002/3000=0.0100.000667=15 (or 101=10)
  2. Interpretation:
    Smokers have a 10 to 15 times higher risk of developing lung cancer compared to non-smokers. Relative Risk measures the strength of association between an exposure and disease in prospective cohort studies.


MNJ11-006
On auditing urine microscopy against urine culture results:

Urine Microscopy Pure Growth (Infection +) Multiple Growth / No Growth (Infection −) Total
>50 WBC (Test +) 95 (A) 15 (B) 110
<50 WBC (Test −) 10 (C) 200 (D) 210
Total 105 215 320
  1. Calculate the Positive Predictive Value (PPV) of urine microscopy.
  2. Calculate the Negative Predictive Value (NPV) of urine microscopy.
  3. Calculate the Sensitivity and Specificity.

Answer

  1. Positive Predictive Value (PPV):
    PPV=AA+B=9595+15=95110=86.36%

  2. Negative Predictive Value (NPV):
    NPV=DC+D=20010+200=200210=95.24%

  3. Sensitivity and Specificity:

    • Sensitivity:
      Sensitivity=AA+C=9595+10=95105=90.48%
    • Specificity:
      Specificity=DB+D=20015+200=200215=93.02%

MNJ11-007

MNJ-P-OSCE 11. Clinical biostatistics_page_6_Picture_2.jpeg

  1. Define Median, 1st Quartile (Q1), and 3rd Quartile (Q3).
  2. Define Rate and Ratio. What is the fundamental difference between them?
  3. What is the primary difference between a Case-Control study and a Cohort study?
  4. What is the difference between Incidence and Prevalence?

Answer

  1. Definitions:

    • Median (Q2): The middle value of an ordered dataset such that 50% of observations fall below and 50% above it.
    • 1st Quartile (Q1): 25th percentile (25% of observations lie below, 75% above).
    • 3rd Quartile (Q3): 75th percentile (75% of observations lie below, 25% above).
  2. Rate vs Ratio:

    • Rate: Numerator is a component/part of the denominator and involves a time dimension (e.g., mortality rate).
    • Ratio: Quantifies the relationship between two independent quantities; numerator is not part of the denominator (e.g., male-to-female ratio).
  3. Case-Control vs Cohort:

    • Case-Control Study: Retrospective; starts from outcome/disease (cases vs controls) and looks backward for antecedent exposures (yields Odds Ratio).
    • Cohort Study: Usually prospective; starts from exposure status (exposed vs unexposed) and follows subjects forward to evaluate disease occurrence (yields Relative Risk and Incidence).
  4. Incidence vs Prevalence:

    • Incidence: Rate of occurrence of new cases in a population at risk during a specified period.
    • Prevalence: Proportion of all existing cases (both old and new) in a population at a specific point in time (point prevalence) or period of time.

MNJ11-008
Calculate the Mean, Median, Mode, Mean Deviation, and Standard Deviation (SD) of the diastolic blood pressure readings given below:

83,75,81,79,71,95,75,77,84,71,75,75,77,79,81,83,84,95

Answer

  1. Mean (x―):
    x―=∑xn=144018=80.0 mmHg

  2. Median:
    Median=x9+x102=79+792=79.0 mmHg

  3. Mode:
    Mode=75.0 mmHg (frequency =4)

  4. Mean Deviation:
    MD=∑|x−x―|n≈5.56 mmHg

  5. Standard Deviation (s):
    s=∑(x−x―)2n−1≈7.02 mmHg (or σ≈6.82 mmHg for population)


MNJ11-009

MNJ-P-OSCE 11. Clinical biostatistics_page_6_Figure_9.jpeg

  1. What is the name of this curve?
  2. What are its uses in clinical medicine and diagnostic testing?
  3. What do the X-axis and Y-axis represent?

Answer

  1. Name: Receiver Operating Characteristic (ROC) Curve.
  2. Uses:
    • Evaluates and compares the diagnostic accuracy of continuous diagnostic/screening tests across all possible cutoff points.
    • Area Under the Curve (AUC / c-statistic) quantifies overall test discrimination power (1.0=perfect, 0.5=chance).
    • Identifies the optimal cutoff threshold that maximizes Sensitivity and minimizes False Positive rate (Youden index).
  3. Axes:
    • Y-axis: Sensitivity (True Positive Rate).
    • X-axis: 1−Specificity (False Positive Rate).

MNJ11-010

MNJ-P-OSCE 11. Clinical biostatistics_page_6_Figure_13.jpeg

  1. What is the name of this chart/graph?
  2. What are its uses?

Answer

  1. Name: Scatter Plot (Scatter Diagram).
  2. Uses:
    • Visually displays the relationship, correlation, and pattern (linear, non-linear, positive, negative, or no association) between two continuous quantitative variables.
    • Evaluates data distribution and identifies outliers prior to linear regression / Pearson correlation analysis.

MNJ11-011
During a study at a hospital, the Peak Expiratory Flow Rate (PEFR) of 100 adolescent boys follows a normal distribution with a mean of 280 L/min, a Standard Deviation (SD) of 30 L/min, and a Standard Error of the Mean (SE) of 2 L/min.

  1. What will be the reference range in which 95% of the boys' individual PEFR values lie in this sample?
  2. What will be the 95% Confidence Interval for the true mean PEFR of the population from which the sample was taken?

Answer

  1. 95% Sample Reference Range:
    Range=Mean±1.96×SD≈280±2(30)=280±60=220 to 340 L/min

  2. 95% Confidence Interval for Population Mean:
    95=Mean±1.96×SE≈280±2(2)=280±4=276 to 284 L/min


MNJ11-012
A study was carried out to assess the diagnostic accuracy of an IgM ELISA test for Leptospirosis compared with blood culture (gold standard) in 100 suspect cases.

Construct the 2x2 contingency table and calculate:

  1. Specificity
  2. Sensitivity
  3. Positive Predictive Value (PPV)
  4. Negative Predictive Value (NPV)

Answer

2x2 Contingency Table:

Test Result Blood Culture (+) Blood Culture (−) Total
IgM ELISA (+) 30 (TP, a) 40 (FP, b) 70
IgM ELISA (−) 10 (FN, c) 20 (TN, d) 30
Total 40 60 100
  1. Specificity:
    Specificity=db+d×100=2040+20×100=2060×100=33.33%

  2. Sensitivity:
    Sensitivity=aa+c×100=3030+10×100=3040×100=75.0%

  3. Positive Predictive Value (PPV):
    PPV=aa+b×100=3030+40×100=3070×100=42.86%

  4. Negative Predictive Value (NPV):
    NPV=dc+d×100=2010+20×100=2030×100=66.67%


MNJ11-013
A new rapid antigen test was compared with blood culture (gold standard) for diagnosing enteric fever in 500 children. Culture was positive in 400 children. Rapid test was positive in 300 children, and both culture and rapid test were positive in 260 children.

Construct the 2x2 table and calculate:

  1. Sensitivity
  2. Specificity
  3. Positive Predictive Value (PPV)
  4. Negative Predictive Value (NPV)
  5. Positive Likelihood Ratio (LR+)
  6. Negative Likelihood Ratio (LR−)

Answer

2x2 Contingency Table:

Test Result Culture Positive (Disease +) Culture Negative (Disease −) Total
Rapid Test Positive 260 (a) 40 (b) 300
Rapid Test Negative 140 (c) 60 (d) 200
Total 400 100 500
  1. Sensitivity: aa+c=260400=65.0%
  2. Specificity: db+d=60100=60.0%
  3. PPV: aa+b=260300=86.67%
  4. NPV: dc+d=60200=30.0%
  5. Likelihood Ratio Positive (LR+):
    LR+=Sensitivity1−Specificity=0.651−0.60=0.650.40=1.625
  6. Likelihood Ratio Negative (LR−):
    LR−=1−SensitivitySpecificity=1−0.650.60=0.350.60≈0.583

MNJ11-014
Write the following journal article reference in standard Vancouver style:

Answer

Vancouver Reference Format:
Author Surname Initials. Title of article. Abbreviated Journal Title. Year; Volume(Issue): Pages.

Formatted Citation:
Bhargava S, Sharma M, Kalra E. Hand grip strength and its relationship with birth weight in adolescent population. Indian Pediatr. 2013; 78: 301-5.


MNJ11-015
Yearly vital statistics data (for year 2000) pertaining to deliveries and outcome in a community is as follows:

MNJ-P-OSCE 11. Clinical biostatistics_page_8_Picture_2.jpeg

Calculate demonstrating all formula steps:

  1. Perinatal Mortality Rate (PMR)
  2. Neonatal Mortality Rate (NMR)

Answer

  1. Perinatal Mortality Rate (PMR):
    PMR=Stillbirths+Early Neonatal Deaths (first week)Total Births (Live births + Stillbirths)×1000
    PMR=80+32010,000×1000=40010,000×1000=40 per 1000 total births

  2. Neonatal Mortality Rate (NMR):

    • Live Births=Total births−Stillbirths=10,000−80=9,920 (or rounded to 10,000)
    • Total Neonatal Deaths=320+180=500
      NMR=Total deaths in first 28 daysTotal live births×1000=50010,000×1000=50 per 1000 live births

MNJ11-016
Match the Oxford Centre for Evidence-Based Medicine (CEBM) Levels of Evidence with their study designs:

Level of Evidence Characteristics
Level I Case series
Level II Lesser quality RCT (e.g., <30% follow-up; no blinding; improper randomization) / Systematic review of Level II RCTs
Level III Expert opinion without explicit critical appraisal
Level IV High-quality RCT with statistically significant difference or narrow confidence interval / Systematic review of Level I RCTs
Level V Case-control study, retrospective comparative cohort study / Systematic review of Level III studies

Answer

Correct Match:


MNJ11-017
Determine the sample size (N) to find out the daily Vitamin A requirement in under-five children of Pune district. From existing literature, the mean daily requirement is documented as 930 IU with a Standard Deviation (SD) of 90 IU. Consider the allowable error / precision (L) as 9 IU.

Answer

Sample Size Formula for Quantitative / Continuous Data (Mean):
N=4×SD2L2=Z1−α/22×σ2L2
(Where Z=2 at 95% confidence level)

SD=90 IU,L=9 IU
N=4×(90)2(9)2=4×810081=4×100=400

Required Sample Size: 400 children.


MNJ11-018
The Peak Expiratory Flow Rates (PEFR in L/min) of 10 children of the same age and height are as follows:

250,260,290,200,240,240,260,270,270,290
  1. What is the Range?
  2. What is the Mean and Mean Deviation?
  3. What is the Standard Deviation (SD)?

Answer

  1. Range:
    Range=Maximum−Minimum=290−200=90 L/min (from 200 to 290 L/min)

  2. Mean (x―) and Mean Deviation (MD):

    • Mean:
      x―=250+260+290+200+240+240+260+270+270+29010=257010=257.0 L/min
    • Mean Deviation:
      MD=∑|x−x―|N=7+3+33+57+17+17+3+13+13+3310=19610=19.6 L/min
  3. Standard Deviation (s):
    ∑(x−x―)2=49+9+1089+3249+289+289+9+169+169+1089=6410
    s=641010−1=712.22≈26.69 L/min(or σ=641≈25.32 L/min)


MNJ11-019

MNJ-P-OSCE 11. Clinical biostatistics_page_8_Figure_15.jpeg

  1. Identify the diagram type.
  2. What is its clinical/statistical use?
  3. Name and interpret each correlation pattern from A to F shown in the figure.

Answer

  1. Diagram: Scatter plots demonstrating different patterns of Correlation.
  2. Use: Visual analysis of the direction, form, and strength of the relationship between two quantitative variables.
  3. Patterns:
    • A: No correlation (r=0).
    • B: Weak / Moderate positive correlation.
    • C: Strong positive correlation (r≈+0.9).
    • D: Weak / Moderate negative correlation.
    • E: Strong negative correlation (r≈−0.9).
    • F: Perfect positive correlation (r=+1.0) or curvilinear/nonlinear relation.