Which statement best describes a positive control in chemical testing?

Which statement best describes a positive control in chemical testing?

• A. Both controls yield the same result
• B. Positive control yields expected result to show test works
• C. Controls are unnecessary in simple tests
• D. Negative control yields no result to detect contamination or drift

Answer: (B)

In chemical testing, a positive control is a sample that is known to produce a positive result under the test conditions. Its role is to confirm that the assay and procedures are working correctly—reagents are active, instrumentation is functioning, and the method can detect the target when it’s present. When the positive control gives the expected positive outcome, you can trust that a true positive in your test samples would be detected. If the positive control fails, the entire run is invalid because something in the method isn’t functioning properly. For context, a negative control, which should show no signal, is used to check for contamination or background drift, and the idea that controls are unnecessary in simple tests isn’t accurate—controls help ensure results are reliable. The notion that both controls yield the same result isn’t correct, since the positive control should yield a positive result while the negative control should yield little or no signal.

In chemical testing, a positive control is a sample that is known to produce a positive result under the test conditions. Its role is to confirm that the assay and procedures are working correctly—reagents are active, instrumentation is functioning, and the method can detect the target when it’s present. When the positive control gives the expected positive outcome, you can trust that a true positive in your test samples would be detected. If the positive control fails, the entire run is invalid because something in the method isn’t functioning properly.

For context, a negative control, which should show no signal, is used to check for contamination or background drift, and the idea that controls are unnecessary in simple tests isn’t accurate—controls help ensure results are reliable. The notion that both controls yield the same result isn’t correct, since the positive control should yield a positive result while the negative control should yield little or no signal.