Overview
This lecture covers the difference between accuracy and precision, using dartboard and laboratory measurement examples to illustrate each concept.
Accuracy vs. Precision: Definitions
- Accuracy is how close a measured value is to the actual (true) value.
- Precision is how close repeated measured values are to each other, regardless of accuracy.
Dartboard Analogy
- Low Accuracy, Low Precision: Darts are far from the bullseye and from each other.
- Low Accuracy, High Precision: Darts are close together but far from the bullseye.
- High Accuracy, Low Precision: Darts are near the bullseye but spread out.
- High Accuracy, High Precision: Darts are tightly grouped at the bullseye.
Laboratory Measurement Examples
- Low Accuracy, Low Precision: All measurements are far from the true value and from each other (e.g., 6.32g, 3.01g, 7.55g, 4.02g for a 5.00g object).
- Low Accuracy, High Precision: Measurements are tightly grouped but far from the true value (e.g., 8.32g, 8.35g, 8.29g, 8.32g).
- High Accuracy, Low Precision: Measurements are near the true value but not close to each other (e.g., 5.15g, 4.77g, 5.28g, 5.00g).
- High Accuracy, High Precision: Measurements are both close to the true value and close to each other (e.g., 5.01g, 4.99g, 5.00g, 5.00g).
Key Terms & Definitions
- Accuracy — How close a measurement is to the true or accepted value.
- Precision — How close repeated measurements are to one another.
Action Items / Next Steps
- Review the dartboard analogy to reinforce the difference between accuracy and precision.
- Practice identifying accuracy and precision in sample laboratory data.