Sample Size Calculation for UK Dissertations
Sample size calculation dissertation UK work should be based on the planned analysis and the research objective. A defensible justification explains the assumptions rather than relying on a universal minimum number.
Identify the Primary Outcome and Test
Decide which research question drives the calculation. A comparison of two means requires different inputs from multiple regression or correlation.
Select the Effect Size or Precision Target
Where power analysis is appropriate, justify the expected effect using evidence. For estimation-focused research, a precision-based calculation may be more meaningful.
Account for Study Design
Repeated observations, clustering, unequal group allocation and expected attrition may change the required recruitment target.
Document the Calculation
Report the software or formula, statistical test, effect size or precision assumption, alpha if relevant, power target and final sample. Explain any inflation for attrition separately.
Avoid Common Errors
- using a rule of thumb without reference to the design;
- calculating sample size after seeing the results;
- choosing an effect size only because it gives a convenient number;
- ignoring attrition or missing data;
- reporting the final number without the assumptions.
Use Sample Size Justification for Dissertation and Sample Size Consultant UK.