Introduction to Biostatistics: Main Exam, 19 July 2023

Mount Kenya University · Department of Community Health, Epidemiology and Biostatistics · Diploma in Dental Technology, Diploma in Community Health · DMA1301

Mount Kenya University Introduction to Biostatistics (DMA1301) 2022-2023 past exam with model answers.

Instructions: ANSWER ALL QUESTIONS IN SECTION A AND ANY OTHER TWO IN SECTION B.

SECTION A:

1. Define the following terms.

  1. a) standard deviation (2.5 marks)
    Model answer
    • Standard deviation: a measure of the average distance of each data point from the mean, indicating the spread or variability of a dataset.
  2. b) Randomization (2.5 marks)
    Model answer
    • Randomization: the process of assigning participants or experimental units to groups by chance, ensuring each unit has an equal probability of any assignment and reducing selection bias.

2. Explain five sources of statistical data (5 marks)

Model answer
  • Surveys/Questionnaires: data collected directly from individuals using structured instruments.
  • Observational studies: data gathered by watching and recording behaviours or events without intervention.
  • Administrative records: data from existing sources such as hospital registers, school enrolments or government databases.
  • Experimental data: data generated from controlled experiments where variables are manipulated.
  • Secondary data: data previously collected for other purposes, e.g., published research, census reports.

3. State importance of diagrammatic representation (5 marks)

Model answer
  • Visual summarisation: diagrams quickly convey patterns, trends and outliers that raw numbers hide.
  • Comparison: side‑by‑side graphs allow easy comparison of groups or variables.
  • Communication: aids understanding for non‑technical audiences and supports presentation of findings.
  • Data checking: plots reveal errors, missing values or abnormal distributions.
  • Decision‑making: visual evidence helps policymakers and clinicians interpret results promptly.

4. Explain three statistical methods. (5 marks)

Model answer
  • Descriptive statistics: summarise data using measures such as mean, median, mode, range and standard deviation.
  • Inferential statistics: draw conclusions about a population from a sample using hypothesis testing, confidence intervals and p‑values.
  • Regression analysis: examine relationships between variables and predict outcomes, e.g., linear or logistic regression.

5. State the uses of statistics. (5 marks)

Model answer
  • Disease monitoring: track incidence and prevalence to guide public‑health interventions.
  • Evaluation of treatments: assess efficacy and safety of dental or medical therapies.
  • Resource planning: inform allocation of personnel, equipment and budgets.
  • Research design: determine sample sizes and power for studies.
  • Policy development: provide evidence for guidelines, regulations and health‑promotion programmes.

6. Highlight how ungrouped data can be presented. (5 marks)

Model answer
  • Univariate presentation: list each observation in a single column.
  • Frequency table: show each value with its count.
  • Cumulative frequency: add counts progressively.
  • Relative frequency: proportion of each value.
  • Graphical display: stem‑leaf plot or dot plot.

7. Describe descriptive statistics. (5 marks)

Model answer
  • Definition: summary of data characteristics.
  • Measures of location: mean, median, mode.
  • Measures of spread: range, variance, SD.
  • Shape indicators: skewness, kurtosis.
  • Visualization: box‑plot, histogram.

8. Explain the difference between statistics and research. (5 marks)

Model answer
  • Statistics: collection, analysis, interpretation of data.
  • Research: systematic inquiry to answer a question.
  • Purpose: statistics provide evidence; research seeks knowledge.
  • Scope: statistics can be applied to any data; research follows a design.
  • Outcome: statistics produce results; research produces conclusions and recommendations.

SECTION B

9. Critique five measures of central tendency. (15 marks)

Model answer
  • Mean: sensitive to outliers; useful for interval/ratio data.
  • Median: robust to extremes; good for ordinal or skewed data.
  • Mode: indicates most frequent value; useful for categorical data.
  • Geometric mean: appropriate for multiplicative processes.
  • Harmonic mean: best for rates or ratios.
  • More answers: trimmed mean, weighted mean.

10. Discuss methods of data collection techniques. (15 marks)

Model answer
  • Surveys: questionnaires, interviews.
  • Observational studies: direct observation, case reports.
  • Experimental methods: randomized controlled trials.
  • Secondary data: existing records, registries.
  • Mixed methods: combine qualitative and quantitative.
  • More answers: focus groups, diary studies, electronic health records.

11. Discuss types used in probability techniques. (15 marks)

Model answer
  • Discrete probability: events with countable outcomes.
  • Continuous probability: events with infinite outcomes.
  • Conditional probability: probability given another event.
  • Joint probability: probability of two events occurring together.
  • Independent probability: events that do not affect each other.
  • More answers: marginal probability, Bayes’ theorem, probability distributions.

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