What is it? Why is it important?

The sample size consists of a subset of individuals selected from a larger population, and who they are meant to represent.

 

The statistical power of a study is directly related to the sample size. In other words, a larger sample size will more accurately represent the population under investigation. Thus, the sample size has a direct effect on the precision and accuracy of study results, including the ability to detect a real effect (e.g. the ability of an interventional drug to lower blood pressure in participant with high blood pressure).  

 

When planning a study, it is important to justify the defined sample size of the study. The study sample size is calculated by the study statistician.

 

What do I need to do?

As a SP-INV, based on the aim of your study explain how the sample size and its subsequent collected data are expected to provide valuable scientific information.

 

Aspects to consider include:

  • The outcome/endpoint of your study (e.g. cholesterol concentration)
  • The method you use for the sample size estimation
  • The statistical framework, which can either be:
    • Hypothesis testing (e.g. you want to test the difference in cholesterol concentration between two patient groups). Define the null and alternative hypothesis
    • Precision-based (e.g. you want to estimate the mean in cholesterol concentration of a certain group of patients). Define the type I error and power
  • The assumption/previous knowledge which were used as a basis for the sample size calculation (e.g. we expect a mean value of 5.2 mmol/L and a standard deviation of 1.5)

Where can I get help?

Your local Research Support Centre↧ can assist you with experienced staff regarding this topic

  • Basel, Departement Klinische Forschung (DKF), dkf.unibas.ch

  • Lugano, Clinical Trials Unit (CTU-EOC), ctueoc.ch

  • Bern, Department of Clinical Research (DCR), dcr.unibe.ch

  • Geneva, Clinical Research Center (CRC), crc.hug.ch

  • Lausanne, Clinical Research Center (CRC), chuv.ch

  • St. Gallen, Clinical Trials Unit (CTU), h-och.ch

  • Zürich, Clinical Trials Center (CTC), usz.ch

References

ICH GCP E6(R3) Guideline – see in particular:

  • Essential records table: documentation statistical consideration
  • 3.11.4.5.4 Monitoring of clinical trials
  • 3.16.2 b Statistical programming
  • Appendix B. The protocol – B.10 Statistical considerations

ICH Topic E9 – see in particular

  • 3.5 Sample Size
  • 4.4 Sample size adjustment

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

  • 5.1 Study population
  • 5.6 Statistical analysis
Abbreviations
  • CTU – Clinical Trials Unit
  • ICH – International Council for Harmonisation
  • ICH GCP – International Council for Harmonisation Good Clinical Practice
  • SP-INV – Sponsor Investigator
Development ↦ Statistic Methodology ↦ Sample Size ↦ Justification
Study
Basic

Provides some background knowledge and basic definitions

Basic Protocol
  1. Research and Ethics
    1. Principles
    2. Ethical Dilemma
  2. Study Protocol
    1. Aim
Basic Management
  1. Study Management
    1. Definition
Basic Ethics and Laws
  1. Principles of Ethics Research
    1. Declaration of Helsinki
    2. Declaration of Taipei
  2. Authorities
    1. Ethics Committee
    2. Swissmedic
    3. Federal Office of Public Health
    4. International
  3. Swiss Law
    1. Human Research Act
    2. Transplantation Act
    3. Stem Cell Research Act
    4. Data Protection Act
  4. Clinical Trials Ordinance
    1. Aim
    2. Medicinal Product Studies
    3. Other Clinical Studies
    4. Transplantation
    5. Transplant Products
    6. Gene Therapy, GMO, Pathogenic
    7. Ionising Radiation
  5. Clinical Trials with Medical Device Ordinance
    1. Aim
    2. Medical Device Studies
    3. In Vitro Diagnostic Medical Device Studies
    4. Ionising Radiation
  6. Medical Device Ordinance
    1. Aim
    2. Notified Bodies
  7. Human Research Ordinance
    1. Aim
    2. Projects with Data and Biological Material
    3. Further-use of Data and Biological Material
    4. Further-use and Informed Consent
    5. Deceased Persons Embryos and Foetuses
  8. Organisation Ordinance
    1. Aim
  9. Human Research Coordination Portal
    1. Human Research in Switzerland
  10. Submission Portal
    1. Ethics Portal BASEC
    2. Swissmedic eGov Portal
  11. Guidelines
    1. Good Clinical Practice
    2. ISO 14155
    3. ISO 20916
Basic Documents
  1. Document Management
    1. Purpose
    2. In Studies
    3. Document Identification
    4. Document Filing
  2. Standard Operating Procedures
    1. Purpose
  3. Working Instructions
    1. Purpose
  4. Logs
    1. Purpose
  5. Essential Documents
    1. Requirement
  6. Certified Copies
    1. Procedures
Basic Safety
  1. Safety Laws
    1. Aim
  2. Safety Terminology
    1. Overview
  3. Safety Data
    1. Product Development
    2. Pre-Clinical Studies
    3. In Clinical Studies
  4. Safety Information
    1. Investigator Brochure
  5. Safety Vigilance
    1. Pharmacovigilance
    2. Materiovigilance
Basic Data Management
  1. Data Management in Studies
    1. Aim
  2. Study Database
    1. Clinical Data Management System
    2. Study Data
    3. Raw Data
    4. Metadata
  3. Regulatory Requirements
    1. Swiss Law
    2. EU Regulation
Basic Statistic Methodology
  1. Statistics
    1. Definition
    2. Statistician Role
    3. Statistical Software
  2. Research Question
    1. Definition
    2. The Population
    3. Intervention and Control Group
    4. Placebo and Comparator
    5. Study Outcome Endpoint
    6. Outcome Endpoint Description
  3. Study Design
    1. Definition
    2. Sample Size Calculation
    3. Randomization
    4. Study Blinding
    5. Interim Analysis
  4. Data Collection
    1. Planning
    2. Predictor Variable
    3. Confounding Variable
Basic Quality and Risk
  1. Risk Management Definitions
    1. Risk-Based Approach
    2. Risk Identification
    3. Risk Evaluation and Prioritisation
    4. Risk Evaluation Matrix
    5. Risk Control Measures
  2. Quality Management System (QMS)
    1. Risk Based
  3. Risk-Based QMS Responsibilities
    1. Sponsor-Investigator
    2. Site-Investigator
    3. Study Staff
Basic Monitoring
Basic Drug or Device
  1. Therapeutic Products
    1. Definition
    2. Generic Products
    3. Complementary and Herbal Medicine
    4. Orphan Drugs
    5. Product Development
    6. Good Manufacturing Practice
    7. Market Surveillance
    8. In Studies
  2. Medicinal Product
    1. Definition
    2. Market Authorization
    3. Manufacturing and Distribution
  3. Medical Device
    1. Definition
    2. Conformity Assessment
    3. Manufacture Responsibility
  4. In Vitro Diagnostic Device
    1. Definition
Basic Biobanking
  1. Definition
    1. Biobank
    2. Biological Material
    3. Specimen / Sample
    4. Pre-Analytical Phase
    5. Data Coding / Anonymisation
    6. Incidental Findings
  2. Donor
    1. In Research
  3. The Swiss Law
    1. Human Research Ordinance
    2. Research with Biological Material
    3. Further Use of Biological Material
    4. Further Use and Informed Consent
  4. Ethics Principles
    1. Declaration of Taipei
  5. Biobanking Standards
    1. ISO Biobanking
  6. Swiss Biobanking Platform
    1. Aim
    2. Services
    3. Quality Labels
Concept

Starts with a study idea

Ends after having assessed and evaluated study feasibility

Concept Protocol
  1. Research Question
    1. Feasibility
Concept Management
  1. Study Idea
    1. Feasibility
    2. Implementation
    3. Design
  2. Resources
    1. Study Staff
    2. Infrastructure
    3. Storage
    4. Partners
    5. Budget
Concept Ethics and Laws
  1. Research Aim
    1. Advancing Science
    2. Marketing Products
  2. Research Integrity
    1. Principles
    2. Conflict of Interest
    3. Participant Protection
  3. Ethics and Regulatory Requirements
    1. Ethics Requirements
    2. Laws and Guidelines
    3. Institution Requirements
    4. Study Compliance
  4. Ethics and Regulatory Advice
    1. Ethics Clarification
    2. Swissmedic Scientific Advice
    3. Swissmedic Pre-Submission
Concept Documents
  1. Required Documents
    1. Protocol and Synopsis
    2. Investigator's Brochure
Concept Safety
  1. Safety in Studies
    1. Risk-Benefit Ratio
    2. Participant Risk-Benefit
  2. Study Risk Categorisation
    1. Procedures
    2. Risk Categories
Concept Data Management
  1. Stakeholders
    1. Sponsor-Investigator
    2. Data Manager
    3. Statistician
    4. Site-Investigator
    5. Monitor
  2. Clinical Data Mgmt. System
    1. Selection
    2. Computer System Validation
  3. Server Management
    1. Data Storage
    2. Back-Up and Recovery
Concept Statistic Methodology
  1. Study Feasibility
    1. Research Question
Concept Quality and Risk
  1. Study Feasibility
    1. Aim
    2. Feasibility Questionnaire
    3. Risk Assessment Form
    4. Study Team
Concept Monitoring
  1. Monitoring
    1. Aim
    2. Study Requirement
    3. Site Qualification
Concept Drug or Device
Concept Biobanking
  1. Biobanking in Studies
    1. Requirement
    2. Quality of Biological Material
  2. Management of a Biobank
    1. Biobank Goverance
    2. Biobank Regulation
    3. Material Transfer Agreement
Development

Starts with confidence that the study is feasible

Ends after having received ethics and regulatory approval

Development Protocol
  1. Formal Structure
    1. Requirements
    2. Protocol Template
  2. Writing the Protocol
    1. Content
    2. Responsibilities
  3. Study Participants
    1. Participant Risks and Benefits
    2. Participant Right
Development Management
  1. Responsibilities
    1. Sponsor-Investigator
    2. Site-Investigator
    3. Staff Qualification and Training
    4. Good Clinical Practice Training
  2. Study Quality
    1. Implementation
  3. Study Safety
    1. Requirement
  4. Study Management
    1. Oversight
    2. Tracking
    3. Infratructure and Maintenance
    4. Multicentre Studies
    5. Insurance
    6. Outsourced Services
    7. Contract
    8. Budget
  5. Study Documents
    1. Protocol
    2. Participant Information Sheet
    3. Informed Consent Form
    4. General Consent
    5. Essential Documents
    6. Source Data
  6. Informed Consent Process
    1. Procedures
    2. Exemption from written Consent
  7. Study Approval
    1. Ethics Committee
    2. Swissmedic
    3. Fed. Off. Public Health
  8. Biobanking
    1. Management
Development Ethics and Laws
  1. Ethics Application
    1. Submission
    2. Application Dossier
    3. Approval
  2. Swissmedic Application
    1. Submission
    2. Application Dossier
    3. Early Clarification Meeting
    4. Late Clarification Meeting
    5. Approval Medicinal Products
    6. Approval Medical Device
  3. Federal Office of Public Health
    1. Submission
    2. Approval
  4. Liability
    1. Insurance
    2. Good Clinical Practice
Development Documents
  1. Required Documents
    1. Study Protocol
    2. Participant Information
    3. Insurance and Contract
    4. Study Documents
    5. Document Submission
Development Safety
  1. Safety Documentation
    1. The Protocol
    2. Study Documents
    3. Data Protection
Development Data Management
  1. Database Development
    1. Variables
    2. Specification
    3. Case Report Form
    4. Calculated Fields
    5. Data Coding and Anonymisation
    6. Data Confidentiality
  2. Data Quality
    1. Requirement
    2. Quality Assurance
    3. Data Mgmt. Plan
    4. Data Monitoring
    5. Data Transfer Agreement
  3. Database Lock
    1. Procedures
Development Statistic Methodology
  1. Statistics in the Protocol
    1. The Hypothesis
    2. Data-Analysis-Set
    3. Primary and Secondary Analysis
    4. Analysis Method
    5. Missing Data
    6. Study Termination Criteria
  2. Analysis Plan
    1. Procedures
  3. Sample Size
    1. Justification
Development Quality and Risk
  1. Study Risk Management
    1. Risk Identification
    2. Risk Evaluation and Prioritisation
    3. Risk Control Measures
    4. Process Verification and Training
  2. Quality Assurance
    1. Aim
    2. Verification
    3. Audit
  3. Quality Control
    1. Aim
    2. Monitoring
    3. Non-Compliance
  4. Risk Communication
    1. Strategy
Development Monitoring
  1. Montoring Strategy
    1. Aim
    2. Risk-Based Monitoring
    3. On-Site Monitoring
    4. Central Data Monitoring
    5. Off-Site Monitoring
    6. Monitoring Plan
Development Drug or Device
Development Biobanking
  1. Biobank Set-Up
    1. Biobank Database
    2. Facilities and Materials
    3. Collection / Storage Containers
    4. Storage Equipment
    5. Equipment Maintenance
    6. Freezer Emergency Plan
  2. Donor Consent
    1. In Clinical Studies
    2. In Research Projects
    3. For Further Use
    4. Communication
  3. Handling of Biological Material
    1. Sample Workflow
    2. Sample Collection
    3. Sample Transport
    4. Sample Reception
    5. Sample Processing
    6. Sample Storage
    7. Sample Distribution
    8. Sample Analysis
  4. Documentation
    1. Forms and Logs
    2. Non-Conformities
  5. Safety
    1. Risk-Based Approach
    2. Donors
    3. Biobanking Staff
  6. Quality Control
    1. Quality Control Indicators
    2. Data Monitoring
    3. Method Validation
Set-Up

Starts with ethics and regulatory approval

Ends after successful study initiation

Set-Up Protocol
  1. Protocol Training
    1. Requirements
Set-Up Management
  1. Registration
    1. Research Transparency
  2. Study Training
    1. Staff Delegation
  3. Document Management
    1. Requirements
  4. Investigational Product
    1. Definition and Handling
  5. Laboratory
    1. Purpose and Requirement
  6. Study Ready for Conduct
    1. Requirements
Set-Up Ethics and Laws
  1. Study Set-Up
    1. Requirements
Set-Up Documents
  1. Required Documents
    1. Staff Training
    2. Staff Qualification
    3. Master and Site File
Set-Up Safety
  1. Safety Management
    1. Safety Management Plan
    2. Emergency Unblinding
  2. Data Safety Monitoring Board
    1. Aim
Set-Up Data Management
  1. Database Release
    1. Requirement
    2. Access Rights
    3. Training
Set-Up Statistic Methodology
Set-Up Quality and Risk
Set-Up Monitoring
  1. Site Initation Visit
    1. Aim
    2. Prerequisite
    3. Preparation
    4. Conduct
    5. Report
Set-Up Drug or Device
Set-Up Biobanking
  1. Regulatory Affairs
    1. Requirement
  2. Staff Management
    1. Requirement
  3. Sample Management
    1. Sample Traceability
    2. Packaging and Shipment
  4. Biobanking in Studies
    1. Procedures
  5. Data Integrity
    1. Data Accuracy
Conduct

Starts with participant recruitment

Ends after the last participant has completed the last study visit

Conduct Protocol
  1. Protocol Amendment
    1. Procedures
Conduct Management
  1. Participant Recruitment
    1. Pre-Screening
    2. Screening and Consent
    3. Documentation
  2. Amendment
    1. Protocol
    2. Patient Information
  3. Responsibility and Oversight
    1. Sponsor and Site-Investigator
    2. Drug and Device Accountability
    3. Compliance
    4. Newsletter
Conduct Ethics and Laws
  1. Study Conduct
    1. Ongoing Tasks
    2. Data Protection
  2. Participant Protection
    1. Requirements
    2. Consent of Vulnerable Participants
  3. Amendment
    1. Type
    2. Submission
    3. Approval
  4. Safety
    1. Requirements
  5. Inspections and Audits
    1. Inspection Conduct
    2. Audit Conduct
    3. Audit Certificate
  6. Premature Study Termination
    1. Rationale
    2. ReportingTimelines
Conduct Documents
  1. Required Documents
    1. Oversight Documentation
    2. Patient File
    3. Source Data
    4. Amendment
Conduct Safety
  1. Safety Risk Review
    1. Aim
  2. Safety Assessment
    1. Medicinal Product
    2. Medical Device
    3. Other Clinical Trials
    4. Research Projects
  3. Safety Reporting
    1. Procedures
    2. Responsibilities
  4. Medicinal Product Safety Reporting
    1. Adverse Event
    2. Serious Adverse Event
    3. (Serious) Adverse Drug Reaction
    4. Suspected Unexpected Serious Adverse Reaction
    5. Advanced Therapies
  5. Medical Device Safety Reporting
    1. Adverse Event / Adverse Device Effect
    2. Serious Adverse Event and Device Effect
    3. Device Deficiency
  6. Research Project Safety Reporting
    1. Serious Events
  7. Safety and Protective Measures
    1. Procedures
  8. Annual Safety Report
    1. Procedures
Conduct Data Management
  1. Data Entry
    1. Requirement
    2. Collection
  2. Data Quality
    1. Responsibility
  3. Amendment
    1. Requirement
    2. Adding Stakeholders
  4. Data Processing
    1. Data Import
    2. Interim Lock
    3. Data Translation
Conduct Statistic Methodology
  1. Interim Analysis
    1. Procedures
Conduct Quality and Risk
  1. Risk Review
    1. Re-Evaluation
    2. Risk Documentation
  2. Deviation Documentation
    1. Note to File
  3. Regulatory Inspections
    1. Conduct
    2. Findings
    3. Corrective and Preventive Actions
Conduct Monitoring
  1. Routine Monitoring Visit
    1. Preparation
    2. Conduct
    3. Findings
    4. Report
    5. Follow-Up
Conduct Drug or Device
Conduct Biobanking
  1. Biobanking Operation
    1. Processes
Completion

Starts with last study visit completed

Ends after study publication and archiving

Completion Protocol
  1. Administrative Tasks
    1. Procedures
Completion Management
  1. Study Closure
    1. Close-Out Visit
    2. Database Lock
    3. Notification of Closure
    4. Lessons Learned
  2. Clinical Study Report
    1. Requirement
  3. Publishing
    1. Study Registries
    2. Scientific Publications
  4. Archiving
    1. Storage
Completion Ethics and Laws
  1. End of Study Notification
    1. Reporting and Liability
    2. Registry Update
  2. Clinical Study Report
    1. Requirement
  3. Publications
    1. Responsibilities
  4. Inspections and Audits
    1. Procedures
  5. Archiving
    1. Requirements
    2. Duration
Completion Documents
  1. Required Documents
    1. Study Closure
    2. Doument Archiving
    3. Document Destruction
Completion Safety
  1. Clinical Study Report
    1. Procedures
Completion Data Management
  1. Final Database Lock
    1. Procedures
  2. Data Export
    1. Data Formatting
    2. Data Sharing
  3. Clinical Study Report
    1. Requirement
  4. Archiving
    1. Requirement
Completion Statistic Methodology
  1. Data Quality Check
    1. Procedures
  2. Data Preparation
    1. Procedures
  3. Data Analysis and Reporting
    1. Procedures
  4. Quality Controls
    1. Procedures
  5. Publication
    1. Statistician Responsibility
  6. Data Sharing
    1. Data Preparation
Completion Quality and Risk
  1. Clinical Study Report
    1. Risk Reporting
    2. Lessons Learned
  2. Archiving
    1. Study Records
Completion Monitoring
  1. Close-Out Visit
    1. Preparation
    2. Conduct
    3. Report
    4. Follow-Up
    5. Archiving
Completion Drug or Device
Completion Biobanking
  1. Leftover Biological Material
    1. For Further-Use
    2. Destruction
  2. Publication
    1. Analytical Results
Current Path (click to copy): Development ↦ Statistic Methodology ↦ Sample Size ↦ Justification