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Research & Biostatistics: High-Yield Notes Physiotherapy

For the AIIMS Physiotherapy entrance exam (and other competitive exams like JAMIA, PGI), Research Methodology and Biostatistics typically carry 10-15% of the weightage. These questions are usually conceptual. Below is a simplified, exam-focused breakdown.

1. Scales of Measurement

Remember the mnemonic NOIR (Nominal to Ratio) to recall the hierarchy from lowest to highest precision.

Scale Keywords/Definition Physiotherapy Examples
Nominal Names, Categories, No Order. Only counting is possible. Gender (Male/Female), Blood Group, Type of CP (Spastic/Ataxic).
Ordinal Ordered categories, Ranks. Differences between ranks are unknown/unequal. MMT Grades (0-5), Ashworth Scale, Glasgow Coma Scale, Pain Severity (Mild/Mod/Severe).
Interval Equal intervals, but NO Absolute Zero (Zero is arbitrary). Temperature (Celsius/Fahrenheit), IQ Scores.
Ratio Highest level. Has a True Absolute Zero. Ratios are meaningful. Range of Motion (Goniometry), Height, Weight, Walking Speed, Age.
Exam Trick: "Temperature" is usually Interval because 0°C doesn't mean 'no heat'. "Kelvin" scale, however, is Ratio. In Physio, MMT is the most common example of Ordinal data.

2. Measures of Central Tendency

Mean (Average)

  • Most commonly used measure.
  • Formula: Sum of observations / Number of observations.
  • Drawback: Highly affected by extreme values (outliers).

Median (Middle Value)

  • The middlemost value when data is arranged in order.
  • Best Use: When data is Skewed or has outliers.
  • Example: In income data or recovery time, Median is better than Mean.

Mode (Most Frequent)

  • The value that repeats the most.
  • Best Use: For Nominal data (e.g., "What is the most common type of shoulder injury?").

3. Sampling Methods

Probability Sampling (Random)

  • Simple Random Sampling: Lottery method. Everyone has an equal chance.
  • Stratified Random Sampling: Population is divided into subgroups (Strata) based on characteristics (e.g., Age, Gender), and then random samples are taken from each stratum. Best for representation.
  • Cluster Sampling: Population is divided into clusters (usually geographic), and whole clusters are selected.

Non-Probability Sampling

  • Convenience Sampling: Selecting patients who are easily available (e.g., patients visiting your specific OP clinic). Most common in clinical research but has high bias.
  • Purposive Sampling: Researcher selects specific subjects based on criteria.

4. Tests of Significance (Kab use karte hain?)

This is the most confusing part for students. Use this cheat sheet:

Test Name When to use it? Example
T-Test (Student's t-test) Comparing Means of 2 Groups. Comparing ROM between Ultrasound Group vs. SWD Group.
Paired T-Test Comparing Means of the SAME Group (Before vs. After). VAS score Pre-treatment vs. Post-treatment in the same patient.
ANOVA (Analysis of Variance) Comparing Means of More than 2 Groups (>2). Comparing pain relief among Group A (IFT), Group B (TENS), and Group C (Placebo).
Chi-Square Test Comparing Categorical/Proportions data (Non-parametric). Association between Gender (M/F) and Frozen Shoulder (Yes/No).
Pearson Correlation (r) To check the relationship between two continuous variables. Relationship between BMI and Knee Pain intensity.

5. Research Designs

Randomized Control Trial (RCT)

  • The Gold Standard for experimental studies.
  • Must have: Randomization + Control Group + Manipulation (Treatment).
  • High internal validity.

Cohort Study (Prospective)

  • Moves Forward in time.
  • Cause → Effect.
  • Start with exposure (e.g., Smokers) and follow up to see if they develop disease (Lung Cancer).

Case-Control Study (Retrospective)

  • Moves Backward in time.
  • Effect → Cause.
  • Start with Disease (e.g., Lung Cancer patients) and look back at history (Did they smoke?).
  • Best for: Rare diseases.

6. Reliability vs. Validity

  • Reliability (Consistency): If you measure the same thing twice, do you get the same result?
    Example: If a goniometer reads 45° today and 45° tomorrow for the same joint position, it is reliable.
  • Validity (Accuracy): Does the tool measure what it is supposed to measure?
    Example: Does the Lachman test actually detect an ACL tear? If yes, it is valid.

Practice Quiz: Research & Biostatistics (10 MCQs)

Click on the option you think is correct to see the answer and explanation.

Q1. Manual Muscle Testing (MMT) grading (0, 1, 2, 3, 4, 5) is an example of which scale of measurement?

Q2. Which measure of central tendency is most appropriate for skewed data (data with outliers)?

Q3. A researcher wants to compare the effectiveness of three different types of exercises (Isometric, Isotonic, Isokinetic) on quadriceps strength. Which statistical test should be used?

Q4. Which of the following variables is an example of Ratio data?

Q5. A study that starts with patients who already have a disease and looks back into their history for risk factors is called:

Q6. To analyze the association between two categorical variables (e.g., Smoking: Yes/No and Lung Cancer: Yes/No), which test is used?

Q7. Which sampling method involves dividing the population into subgroups based on characteristics (e.g., Age) and then randomly selecting from each?

Q8. Reliability refers to:

Q9. What is the Type I error in hypothesis testing?

Q10. Which is the highest level of evidence in the hierarchy of research designs?

References

  1. Kothari, C. R. (2004). Research Methodology: Methods and Techniques. New Age International.
  2. Portney, L. G., & Watkins, M. P. (2009). Foundations of Clinical Research: Applications to Practice. Pearson/Prentice Hall.
  3. Mahajan, B. K. (2010). Methods in Biostatistics for Medical Students and Research Workers. Jaypee Brothers.

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