Group items tagged

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.

GPS jammers send out a radio signal that’s the same frequency as the satellite signal. Since GPS satellite signals are weak, a GPS jamming device that puts out approximately 2 watts is sufficient to disrupt a GPS signal in a vehicle that’s approximately within 10 feet of the device. This leaves the in-vehicle system unable to establish its position and report back to a GPS tracking center, where the vehicle is registered. There are also fears that terrorists can use these devices to disrupt air traffic and cause severe safety and economic damage to the US. More powerful jammers could disrupt GPS signals in close proximity of airports, causing safety concerns. Our military overseas use GPS extensively to record their position as well as the position of the enemy. With GPS jamming devices in the hands of our enemy, U.S. and allied forces can be severely impacted when launching ground and air-strikes.