UNC Investigator Initiated Studies
A study which involves quantitative research methods will need to have a statistical signoff from the statistician who will be responsible for the design and statistical analysis for that study. The purpose of the signoff is to ensure that the protocol has adequately addressed all relevant study design and quantitative (or statistical) matters and is therefore ready for a rigorous review by a PRC statistician. This includes smaller studies, such as those that are sometimes referred to as ‘feasibility’ or ‘pilot’ studies. A smaller study does not abrogate the need for justification. More about small studies
Most researchers are familiar with the use of power and sample size calculations that are used for the statistical justification for a comparative study that tests a primary research hypothesis. However, not all studies are about hypothesis testing. Sometimes the researcher may be interested in estimating a parameter of interest. In this case, the ‘precision’ of this estimate would provide the statistical justification for the study. In a study’s protocol, there should be a measurable ‘something’ that informs whether the study was ‘successful’ or not. It is critical that the PRC reviewers be able to easily see what defines and makes a study a success, and how this success was measured.
A Note Concerning Qualitative Research Designs
Qualitative research involves the process of collecting, analyzing, and interpreting non-numerical data. A study gathering information using focus groups is an example of a study using qualitative research methods. Obviously, this is very different from the quantitative expertise that statisticians have and use. Qualitative studies require a signoff, but not a statistical (or quantitative) signoff. Please contact the PRC coordinator Stacy Maxwell for further clarification concerning a signoff for a qualitative study.
For expertise in qualitative research, a good place to start would be the UNC Lineberger CHAI Core. This is a shared resource which provides qualitative research specialists.
Another place on campus that may be of interest is the Odum Institute for Research in Social Science. They regularly offer courses on qualitative research methods, such as their Introduction to Focus Groups short course.
A Note Concerning the Statistical Signoff
While quantitative protocols submitted to the PRC for review require a statistical signoff, that signoff need not come from a BIOS SR statistician. BIOS SR statisticians are uniquely qualified to assist LCCC members, since they have extensive experience in designing studies that meet the standards required to pass the rigor of PRC Review.
However, if a BIOS SR statistician hasn’t been a collaborator in the design of the study, or will not be overseeing the analyses, and/or will not be a co-author on manuscripts from the study, then they should not take responsibility for, and signoff on, that study. The person who is be responsible for the design and analysis of a study should be the one to sign the statistical signoff.
It is highly recommended that this person be a trained statistician, but it need not be a BIOS SR statistician. For any questions please email: LCCC_BIOS@med.unc.edu
The following describe ‘feasibility’ and ‘pilot’ studies. It should be noted that many small studies contain aspects of both.
A ‘feasibility’ study is a small study that is often conducted to see if some aspect of the proposed research is ‘doable.’ For example, an investigator may want to see if a questionnaire can be completed by patients at a particular time point during their treatment. The primary measure of success for this feasibility project would be the proportion of completed questionnaires. The measure of precision for this objective would be the width of the 95% confidence interval of this proportion.
A ‘pilot‘ study is a small study with a sample size of often no more than 5 to 15 subjects. A pilot study is often done as a precursor to a larger study. While data from a small study of this kind rarely produces results that are publishable, these studies may gather crucial information that will be used in power and sample size calculations for a larger study and may also provide important insight into study design considerations. Regardless, a pilot study must still contain a clear primary objective and a description of what constitutes a successful completion of the study. A successful pilot study may gather important estimates about measures of interest and their statistical variability. Again, these numbers would be useful in future power and sample size calculations.
Often, a small study will contain components of both these studies. Sometimes these studies may be referred to as ‘exploratory’ studies. The main point to remember is that studies, regardless of size, must have a definition of success that is clear and measurable, and must have some justification for the sample size.