The terms uncertainty and accuracy are often used interchangeably in everyday language, but in the context of measurements and calibration, they have distinct meanings. Here's a breakdown of the difference between the two:

Accuracy:

• Definition: Accuracy refers to how close a measured value is to the true or accepted value of the quantity being measured.

• Context: It's a measure of the correctness of a measurement. For example, if you're measuring the temperature of water, and the true value is 100°C, and your measurement is 100°C, your measurement is accurate.

• Key Idea: A measurement is accurate if it is close to the true value or the accepted standard value.

  Example:

• True Value: 50°C

• Measured Value: 50.1°C
  In this case, the measurement is accurate because it is very close to the true value.

Uncertainty:

• Definition: Uncertainty refers to the range or margin within which the true value of a measurement is expected to lie. It quantifies the doubt or variability associated with a measurement result.

• Context: Uncertainty considers all the potential errors or sources of variation in the measurement process, including instrument precision, environmental conditions, or human factors. It provides a range (or interval) to show how confident we are in the measurement.

• Key Idea: Uncertainty describes the degree of confidence or reliability of a measurement, and it is typically expressed as a ± value (e.g., ±0.5°C, ±0.1%).

  Example:

• Measured Value: 50°C

• Uncertainty: ±0.2°C
  The measurement is reported as 50°C ± 0.2°C, meaning the true value is expected to be between 49.8°C and 50.2°C with a high level of confidence.

Key Differences:

• Accuracy focuses on how close the measurement is to the true value.

• Uncertainty focuses on the degree of doubt or range within which the true value is likely to lie based on the measurement method.

A Simple Analogy:

Imagine you're trying to throw darts at a target.

• If your darts land very close to the bullseye, you're accurate.

• If the darts land all over the target, but you know the range of where they might land (say ±2 inches), you are describing the uncertainty of your aim.

In Practice:

• A measurement can be accurate but imprecise (if it is consistently close to the true value but has large uncertainty in each measurement).

• A measurement can also be precise but inaccurate (if it's consistently the same, but far from the true value).

• The goal is often to reduce both uncertainty and inaccuracy to improve measurement quality.