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[求助]
什么是negative control 什么是positive control？
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| 什么是negative control 什么是positive control？ |
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TrickyVick
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举个例子， 你要测样品X里面有没有物质X Postive就是你把一定量的X加到确定没有X的溶液里做的样品 Negative就是你加的确定没有X的样品 Positive用来确定你的检测方法能否检测到物质X （一面方法不对或机器损坏造成的无法检测的情况） Negative用来确定你检测方法是否有相应的无关信号对应X ,比如某种杂质跟X在一个时间出来，那么你就需要在最后计算样品量的时候减去这个量。 |
8楼2013-03-26 17:08:03
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2楼2013-03-25 22:42:16
XiaOliAngeR
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Negative Negative controls are groups where no phenomenon is expected. They ensure that there is no effect when there should be no effect. To continue with the example of drug testing, a negative control is a group that has not been administered the drug. We would say that the control group should show a negative or null effect. If the treatment group and the negative control both produce a negative result, it can be inferred that the treatment had no effect. If the treatment group and the negative control both produce a positive result, it can be inferred that a confounding variable acted on the experiment, and the positive results are likely not due to the treatment. [edit]Positive Positive controls are groups where a phenomenon is expected. That is, they ensure that there is an effect when there should be an effect, by using an experimental treatment that is already known to produce that effect (and then comparing this to the treatment that is being investigated in the experiment). Positive controls are often used to assess test validity. For example, to assess a new test's ability to detect a disease, then we can compare it against a different test that is already known to work. The well-established test is the positive control, since we already know that the answer to the question (whether the test works) is yes. Similarly, in an enzyme assay to measure the amount of an enzyme in a set of extracts, a positive control would be an assay containing a known quantity of the purified enzyme (while a negative control would contain no enzyme). The positive control should give a large amount of enzyme activity, while the negative control should give very low to no activity. If the positive control does not produce the expected result, there may be something wrong with the experimental procedure, and the experiment is repeated. For difficult or complicated experiments, the result from the positive control can also help in comparison to previous experimental results. For example, if the well-established disease test was determined to have the same effectiveness as found by previous experimenters, this indicates that the experiment is being performed in the same way that the previous experimenters did. When possible, multiple positive controls may be used - if there is more than one disease test that is known to be effective, more than one might be tested. Multiple positive controls also allow finer comparisons of the results (calibration, or standardization) if the expected results from the positive controls have different sizes. For example, in the enzyme assay discussed above, a standard curve may be produced by making many different samples with different quantities of the enzyme. From: http://en.wikipedia.org/wiki/Scientific_control |
5楼2013-03-25 23:08:08
