Issue link: https://www.massageandbodyworkdigital.com/i/68175
such a way that new data is presented. Therefore, it can be considered a primary source of information rather than a secondary source. A tertiary source is based on secondary information, providing an overview of topics. Typical tertiary sources include indexes, encyclopedias, databases, etc. Textbooks can be considered tertiary information, unless they rely exclusively on primary information.8, 9 A tertiary PRIMARY, SECONDARY, AND TERTIARY SOURCES Sources of information are considered primary, secondary, or tertiary depending on originality and proximity. Is the work original, or is the author commenting on the work of others? How close is the author to the source—is this a fi rsthand account or somewhat removed from the research? The distinctions are not rigid; it is not always easy to distinguish between a primary, secondary, or tertiary source of information.1, 2, 3 A primary reference includes original research. In scientifi c literature, a primary source of information is the original publication of a scientist's new data, results, and theories. An author citing this level of information is required to interact with the research and extract information directly.4, 5 A secondary source represents an accounting of the primary data. The original information has been interpreted, analyzed, synthesized, or evaluated by a second party. In a research review, for example, the author restates the original data with a discerning eye, synthesizing a collection of data from a variety of like studies.6, 7 A meta-analysis is a bit different than a research review. Even though it is a culmination and summary of many like-research studies, it also presents original theories and combines data in source is a retelling of information summarized by someone other than the original author—in other words, it is third-hand information. A common pitfall in citing sources is that an author will cite a textbook—at best a secondary source of information—rather than looking up the reference and drawing his or her own conclusions. When you cite a primary source, you demonstrate that you engaged with the original data and considered its hypothesis, methods, and results in context, therefore making the quote more substantial. When you cite a textbook, you are assuming that the author is accurately representing the original research and not quoting it out of context to support a specifi c theory. LEVELS OF EVIDENCE The level of evidence, or the grade we place on the research design, depends on several factors such as generalizability or power, bias, and the presence of comparison or control groups. Studies that provide information applicable to a large group of people are considered to have greater power than small studies that cannot be generalized beyond the subject pool. A study with 500 subjects, for example, is more likely to provide data that is transferable to people over and above those studied verses a study with one subject.10 Controlling for bias is about limiting the possibility that research results could be caused by chance or by something other than the intervention. 118 massage & bodywork july/august 2010 For example, a well-designed research study does not permit the participants to select the protocol they will receive. If given a choice between massage and acupuncture, for example, and people already believe massage will work for them, choosing massage as their intervention can infl uence the treatment's success. They believe they picked the best treatment and may skew reporting as a result. Research has shown that selection bias can boost the power of the treatment.11 A control group or placebo is used to measure the body's natural ability to heal. It is always possible that the subject would have gotten better anyway over the course of time, and this must be accounted for in a study. This is not a fail-safe measure. Placebos have been known to advance healing. In fact, often the evidence demonstrates no statistical difference between the protocol and the placebo.12, 13 When gathering primary references, select research that represents a higher level of evidence than other studies on similar topics with comparative results. Another option is to provide multiple sources for one statement. Citing more than one source for a single piece of information will allow you to cite a wider range of evidence and include lower level studies without diminishing the overall quality of references. DUE DILIGENCE It's important that authors cite the best available evidence. Authors must investigate both the data that supports their theories and the data that contradicts their theories. Then, the author can determine if the information being presented is representative of the current prevailing fi ndings. Consider whether the data has been reproduced in quality studies or is an obscure idea or a theory that has been refuted in more contemporary studies. Other alternatives are possible: that the author's theory has yet to be properly challenged by academic debate or that