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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.
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.
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阴性控制negative control
阳性控制positive control
阳性对照即是100%出现该结果的“实验”组，材料是确定的；
阴性对照则是肯定不会出现结果的“实验组”，材料也是确定的；
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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。
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References
- Biocompare Bench Tips: Improve Western Blots by Including a Positive Control. Posted Aug 7, 2013.
- Western blotting guide and troubleshooting. MD Biosciences.
- European Monoclonal Antibodies Network (Euro MabNet). Antibody Validation: Practical Guide to Finding and Validating Suitable Antibodies for Research.
http://ecyouthdiversion.ca/what-to-do-about-positive-control-and-negative-control-in-biology/
https://www.licor.com/bio/guide/westerns/control_samples