 The Ubiquitous p<.05: Practical versus Statistical Significance Revisited
Connie C. Schmitz, PhD
University of Minnesota Medical School, Department of Surgery
I am not a statistician, but a frequent consumer and purveyor of statistics. My interest in statistics concerns their use in surgical education and research: how can we best apply statistics in a clear-headed versus rote manner? I am drawn to the notion that the purpose of statistics is “to organize a useful argument from quantitative evidence, using a form of principled rhetoric.”1 Statistical analysis has a narrative role to play in our work. But to tell a good story, it has to make sense.
This article is for the non-lover of statistics who wants to learn how statistical analysis can help to tell a good story, and wants to be able to tell that story if called upon to do so. It will focus on one of the core tenets in our belief system, which also turns out to represent a long-standing controversy in the statistical community. That tenet involves the practice of (some would say single-minded, blind-sided, slave-like devotion to) null hypothesis significance test-ing (NHST) and the use of p<.05 as the break-point for determining “significant” findings. The article will also discuss and advocate for using measures of effect size to examine the strength of our alternative hypotheses and to judge the practical significance of our findings. Throughout, I rely on three excellent articles, one by Roger Kirk2 and two by Jacob Cohen,3,4 and a number of accessible texts that are listed among the references. Let’s start by reviewing some basics.
To View this article in full: http://www.facs.org/education/rap/schmitz0207.html
Eradication of Cross-Contaminated Cell Lines: A Call for Action
by
Roland M. Nardone, PhD1
Summary
The use of cross-contaminated cell lines in cancer and other biomedical research is at a high level and increasing. Consequently, a significant proportion of the literature using cell lines is misleading or false, tainting up to 20% of publications. What are the consequences?
1. The wastage of funds on biomedical research that is flawed and often misleading. Millions of dollars are spent on research using false cell lines every year worldwide.
2. Many scientists believe or claim that they are working with cells derived from one tissue, when they either know or could easily find out that the cells are derived from a different tissue. This situation is unnecessary, unacceptable and the antithesis of fundamental scientific principles.
3. Loss of public support for biomedical science. The longer the current situation continues, the more likely it is to damage the credibility of biomedical science and risk the loss of public funding.
In the past, there were excuses for the use of cross-contaminated cell lines. Now, standardized simple inexpensive methods are available to detect and eradicate the problem. We must take action now.
Preamble
Extensive cross-contamination of human and animal cell cultures with a variety of human and animal cell lines is a long-standing problem. Although extensive awareness dates back to the 1950’s, the problem is not diminishing. Estimates based on submission of cell lines to major repositories indicate that up to 20% of the cultures may be cross-contaminated. As continuous cell lines increase in use and as immortalization of cell lines becomes more common the problem will become exacerbated unless strong, realistic measures are taken to correct the situation.
The Consequences and Why Cross-Contamination Needs to be Eliminated
This “white paper” outlines major initiatives which, when applied in concert, could rapidly diminish the problem. These initiatives call for cell line authentication as a condition for receipt of grant funds from major agencies (NIH, NSF, HHMI, ACS, etc.), authentication as a condition for publication of cell culture-based research in leading journals, and focused education opportunities for technicians and scientists regarding prevention and detection of cross-contamination.
The importance, the breadth, and the complexity of the subject require broad participation in the evaluation and possible modification of the strategies outlined herein, as well as due consideration of alternative strategies. Hence, a suitable conference, to evaluate these strategies is recommended.
To view this article in its entirety, please visit: http://ori.hhs.gov/education/CellContamination.shtml
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