Overview
This lecture introduces positive controls in experimental design, explaining their importance for validating negative results and ensuring measurement reliability.
Positive Controls in Experiments
- Positive controls are interventions where an effect is expected, confirming the experiment setup works.
- They help verify that a negative result is truly negative, not due to measurement error.
- Example: Adding a proven energy drink to an activity study ensures activity can be detected if present.
Examples of Positive Controls
- In enzyme assays, a known amount of enzyme serves as a positive control to verify assay accuracy.
- In human experiments, a "gold standard" method (like blood culture for bacteremia) can serve as a positive control when validating a new test.
- Positive controls can also be used for calibrating instruments by comparing to a known result.
Comparing to Negative Controls
- Negative controls show what happens when no effect is expected (e.g., no enzyme present).
- Both positive and negative controls are needed to accurately interpret experimental results.
Additional Uses of Positive Controls
- Positive controls help determine dose response by providing a maximum effect for comparison.
- Solely using negative controls can miss crucial data and reduce experiment reproducibility.
- Positive controls should be planned before starting any experiment.
Key Terms & Definitions
- Positive control — a part of an experiment where a known effect is expected, used to confirm the experimental system works.
- Negative control — a part of an experiment where no effect is expected, ensuring positive results are valid.
- Gold standard — a well-established method or test used as a benchmark for new tests.
Action Items / Next Steps
- Plan and include positive controls in future experimental designs.
- Review past experiments for proper use of both positive and negative controls.