The Difference between Precision & Accuracy

Most of you might already know this, but accuracy is preeminent to the cold chain cycle. If you are considering setting up a quality improvement system that implies gathering data to control or to monitor changes in your process, then this article might be of your interest.

As said, accuracy plays a crucial role in the cold chain cycle. However, there’s a delicate difference between accuracy and precision. Accuracy is defined as the difference between the measurement and the actual true value, while precision refers to how close repeated measurement values are to each other, using the same equipment. In other words, precision refers to how reproducible the measurements can be.

For example, you could be using a thermometric instrument to test X number of temperature equipment. You have identified your target temperature points and you are starting your assessment. When gathering data, the measurements on your equipment are close to each other. This approach implies repeating the same measurements using the same device, as well as trying to replicate the results closer to each other with less variations. In this case, the measurement process used is precise. Conversely, you could be using an accurate thermometric instrument that is taking multiple measurements, with results that are closer to the targeted value, but with a much larger variance. Therefore, the method used is accurate.

See image reference below, to help illustrate the two concepts:

When applying this knowledge to your daily operations, it is important to ensure that your system for collecting measurements isn't flawed. After all, if you can’t rely on your measurement equipment, then the data produced won’t be trustworthy.

Failing to apply these two concepts, can result in unsatisfactory data collection, affecting the final outcome of your analysis. Whenever considering setting up a quality improvement system, it is always best to focus on improving your system before relying on your data.

So how do you determine if your measuring system is faulty? The answer is calibration. Precision and accuracy can be evaluated through different measuring instruments, many measurement analysis tools are accessible and can help identify if an equipment needs to be adjusted. In the cold chain industry, it is important to understand how your temperature instrument tools behave. In example, thermometer readings are usually more reliable within a certain range of temperature, but once outside their recommended temperature range, they can give inaccurate values, yet still be precise. When calibrating an instrument, it is important to assess how far off the measurement is to the true value and it's inherent uncertainties. This is why we always recommend calibrating your equipment periodically to ensure it’s accuracy and precision readings. Also note that when using your equipment, handling of it and storage conditions may affect the measurement quality and reliability over time.

Tips for remembering the difference between Precision & Accuracy

• Precision is how close the values are to each other
  

• Precision is how repeatable a measurement is to the first one (without being near the true value).

• Accuracy is how close the values are to the true value