Statistical validation of results, as Shaffer described it, simply involves testing the null hypothesis: that the pattern you detect in your data occurs at random. If you can reject the null hypothesis—and science and medicine have settled on rejecting it when there's only a five percent or less chance that it occurred at random—then you accept that your actual finding is significant.
The problem now is that we're rapidly expanding our ability to do tests. Various speakers pointed to data sources as diverse as gene expression chips and the Sloan Digital Sky Survey, which provide tens of thousands of individual data points to analyze. At the same time, the growth of computing power has meant that we can ask many questions of these large data sets at once, and each one of these tests increases the prospects than an error will occur in a study; as Shaffer put it, "every decision increases your error prospects." She pointed out that dividing data into subgroups, which can often identify susceptible subpopulations, is also a decision, and increases the chances of a spurious error. Smaller populations are also more prone to random associations.
In the end, Young noted, by the time you reach 61 tests, there's a 95 percent chance that you'll get a significant result at random. And, let's face it—researchers want to see a significant result, so there's a strong, unintentional bias towards trying different tests until something pops out.
Young went on to describe a study, published in JAMA, that was a multiple testing train wreck: exposures to 275 chemicals were considered, 32 health outcomes were tracked, and 10 demographic variables were used as controls. That was about 8,800 different tests, and as many as 9 million ways of looking at the data once the demographics were considered.
anonymous on 10 Apr 15Ergonomic Wheelchair is a light-weight Wheelchair. Its ergonomically designed manual wheelchair built for comfort, health and durability. It uses the patented S-Ergo seat design that helps in distributing weight evenly and reduces the potential for bed sores.Ergonomic wheelchair provides users with a large selection of ultra lightweight wheelchairs that can help improve your life. This series has features that include a high strength lightweight frame, foldable and easy to store, breathable anti-bacterial, anti-staining, removable and machine washable cushion. Ergonomic Wheelchair features an ergonomic "S" shaped seat and the karma ergolite 2501,karma S-106,karma S-105 all features are S-shaped provides the perfect shape to fit the human body to relieve pressure, increase stabilization, weight distribution and lower the risk of pressure sores andscoliosis.Ergonomic Wheelchair users commonly experience pain in their hands and wrists associated with the repetitive stress of wheelchair propulsion. The objectiveof this research was to examine the effect of an ergonomic wheelchair handrim as an intervention designed to reduce pain in the hands and wrists. Ergonomics is the relationship of the body to work. It has long been a priority in industrial settings like assembly plants where work injury from physical overuse is a great danger. Now that computers are causing a lot of physical discomfort, the term is more widely heard.Ergonomic Wheelchairs (Intelligent s-shaped ergonomic seating) provides efficient pressure relief by spreading weight over a greater area, at the same time provides stabilization and reduced sliding. karma ergolite 2501 is the main fetures of the ergonomic wheelchair.It is designed ergonomically, and the backrest angle, backrest height, handlebar height and foot height are adjustable to individual requirements of the user. The optional handrail is designed for quick release and ease of use.Karma ErgoLite is a Lightweight ergonomic wheelchair
