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The false positive rate (FPR) is the proportion of all negatives that still yield positive test outcomes, i.e., the conditional probability of a positive test result given an event that was not present. The false positive rate is equal to the significance level. The specificity of the test is equal to 1 minus the false positive rate.
To administer the test, a user simply has to mix the chemicals with a particle of the suspected substance; if the chemicals turn purple, this indicates the possibility of marijuana. But the color variations can be subtle, and readings can vary by examiner. It was adopted in the 1950s by the United Nations as the preferred test for cannabis ...
The Duquenois reagent is used in the Rapid Modified Duquenois–Levine test (also known as the simple Rapid Duquenois Test), which is an established screening test for the presence of cannabis. The test was initially developed in the 1930s by the French medical biochemist Pierre Duquénois (1904–1986) and was adopted in the 1950s by the ...
Use of marijuana during pregnancy heightens the risk of prematurity, low birth weight and the likelihood of intensive care, a new study found.
More and more people are using marijuana before or during pregnancy to ease nausea, pain, stress and help with sleep. In fact, research found that use has more than doubled in the last two decades
False negative readings can occur when testing is done too early. hCG levels rise rapidly in early pregnancy and the chances of false negative test results diminish with time (increasing gestational age). [22] Less sensitive urine tests and qualitative blood tests may not detect pregnancy until three or four days after implantation. [23]
For alcohol, the cutoff is uniform: A blood alcohol concentration above 0.08 percent. But there is no standard cutoff for THC, the psychoactive compound in marijuana.
For example, the Kastle–Meyer test will show either that a sample is not blood or that the sample is probably blood, but may be a less common substance. Further chemical tests are needed to prove that the substance is blood. Confirmatory tests are the tests required to confirm the analysis. Confirmatory tests cost more than simpler ...