Book contents
- Frontmatter
- Contents
- Editorial board
- Acknowledgements
- List of contributors
- Introduction
- Part I
- 1 The ethics of clinical research
- 2 Research ethics committees and the law
- 3 The regulation of medical research: a historical overview
- 4 The regulation of medical research in the UK
- 5 Observational and epidemiological research
- 6 Social survey research
- 7 Approaching qualitative research
- 8 Complementary and alternative medicine: challenges for research ethics committees
- 9 The ethical review of student research in the context of the governance arrangements for research ethics committees
- 10 The ethics of genetic research
- 11 Research or audit?
- 12 Randomised controlled trials
- 13 Determining the study size
- 14 Risk assessment for research participants
- 15 Absorbed radiation in patient and volunteer studies submitted to the ethical committee: a memorandum
- 16 A guide to the use of radioactive materials and radiological procedures for research purposes
- 17 Indemnity in medical research
- 18 The prevention and management of fraud and misconduct: the role of the LREC
- 19 Understanding clinical trials: a model for providing information to potential participants
- 20 The law relating to consent
- 21 Writing information for potential research participants
- 22 The law relating to confidentiality
- 23 Research involving vulnerable participants: some ethical issues
- 24 The ethics of research related to healthcare in developing countries
- Part II
- Index
13 - Determining the study size
Published online by Cambridge University Press: 08 January 2010
- Frontmatter
- Contents
- Editorial board
- Acknowledgements
- List of contributors
- Introduction
- Part I
- 1 The ethics of clinical research
- 2 Research ethics committees and the law
- 3 The regulation of medical research: a historical overview
- 4 The regulation of medical research in the UK
- 5 Observational and epidemiological research
- 6 Social survey research
- 7 Approaching qualitative research
- 8 Complementary and alternative medicine: challenges for research ethics committees
- 9 The ethical review of student research in the context of the governance arrangements for research ethics committees
- 10 The ethics of genetic research
- 11 Research or audit?
- 12 Randomised controlled trials
- 13 Determining the study size
- 14 Risk assessment for research participants
- 15 Absorbed radiation in patient and volunteer studies submitted to the ethical committee: a memorandum
- 16 A guide to the use of radioactive materials and radiological procedures for research purposes
- 17 Indemnity in medical research
- 18 The prevention and management of fraud and misconduct: the role of the LREC
- 19 Understanding clinical trials: a model for providing information to potential participants
- 20 The law relating to consent
- 21 Writing information for potential research participants
- 22 The law relating to confidentiality
- 23 Research involving vulnerable participants: some ethical issues
- 24 The ethics of research related to healthcare in developing countries
- Part II
- Index
Summary
On most Ethics Committee application forms there is a question asking how the size of the study was determined. This is an important question as study size has ethical implications. Studies that are too small tend to give inconclusive results; they waste money and time, and study participants are inconvenienced. They can give inaccurate answers, which jeopardise future research. An apparently large effect found in a small trial may make a further trial unethical. Conversely, important true effects may be missed.
Usually a formal study size calculation has to be made and the answers to this question on the form are amongst the most complicated to understand. Sometimes confidence intervals are used to explain the study size (usually for descriptive rather than comparative studies) and these are discussed at the end of this chapter. Formal study size calculations are used when the purpose of the study is to compare two or more groups of subjects. There are five areas that must be considered:
Difference of interest
Variability of measurements
Significance level (p-value)
Power of the study to detect a difference
The proportion of the study population that is ‘exposed’ or taking the treatment
People without a statistical training may find it difficult to assess the study size statements and will have to rely on a statistician. However, they can assess whether the difference of interest seems reasonable.
- Type
- Chapter
- Information
- Manual for Research Ethics CommitteesCentre of Medical Law and Ethics, King's College London, pp. 64 - 66Publisher: Cambridge University PressPrint publication year: 2003