What is it? Why is it important?

The study design is the overall strategy used to integrate all different study components needed to answer a study question.

Many study designs exist but most can be divided into:

  • Exploratory research: used to investigate a problem that is not clearly defined
  • Observational research: observe and describe a situation without influencing its outcome
  • Causal research: evaluate the impact of a specific change on existing norms and assumptions


The aim and complexity of a study can affect the choice of study design that must be implemented. The use of study design does again significantly affect:

  • Resources and expertise required
  • Number of required participants
  • Time needed to complete the study
  • Budget, as more procedures, staff, trainings, including data collection procedures become necessary

What do I need to do?

The study must be operationally feasible, thus select the least complex study design needed to answer your study question:

  • Avoid unnecessary complexity and procedures
  • Ensure study documents are clear, concise, and consistent
  • Ensure that collected data, whether electronic or paper CRF reflect specifications given in the study protocol
  • Select the minimum of required variables to answer your study question

For more information refer to Statistics in this Study Guide.


Only variables contributing to the answer of your study question will be useful. Collection of nice to have but not required data will only increase study complexity and consequently required staff, data monitoring and finally budget.

Where can I get help?

Your local CTU can support you with experienced staff regarding this topic


ICH GCP E6(R2) – see in particular guideline

  • 5.4 Trial design


ICH Topic E9 Statistical principles for clinical trials - see in particular guideline

  • 3 Trial design consideration


ICH Topic E8 (R1) General considerations for clinical studies – see in particular guideline

  • 2.2 Scientific approach in design and analysis


ISO 14155:2020 Medical devices (access liable to costs) - see in particular section

  • 6.3 Justification for the design
  • CTU – Clinical Trials Unit
  • eCRF – electronic Case Report Form
  • ICH – International Council for Harmonisation
  • ICH GCP – International Council for Harmonisation - Good Clinical Practice
  • ISO – International Organization for Standardization
  • pCRF – paper Case Report Form
Concept ↦ Management ↦ Study Idea ↦ Design

Provides some background knowledge and basic definitions

Basic Protocol
Basic Statistics
Basic Monitoring
Basic Drug or Device
Basic Biobanking

Starts with a study idea

Ends after having assessed and evaluated study feasibility

Concept Protocol
Concept Statistics
Concept Drug or Device
Concept Biobanking

Starts with confidence that the study is feasible

Ends after having received ethics and regulatory approval

Development Protocol
Development Statistics
Development Drug or Device
Development Biobanking

Starts with ethics and regulatory approval

Ends after successful study initiation

Set-Up Protocol
Set-Up Ethics and Laws
Set-Up Statistics
Set-Up Quality and Risk
Set-Up Drug or Device
Set-Up Biobanking

Starts with participant recruitment

Ends after the last participant has completed the last study visit

Conduct Protocol
Conduct Statistics
Conduct Drug or Device
Conduct Biobanking

Starts with last study visit completed

Ends after study publication and archiving

Completion Protocol
Completion Statistics
Completion Drug or Device
Completion Biobanking
Current Path (click to copy): Concept ↦ Management ↦ Study Idea ↦ Design

Please note: the Easy-GCS tool is currently under construction.