Precision refers to the agreement between the measured quantities obtained from replicating measurements of the same or similar objects in specified conditions.

Precision is not a quantity, so it cannot be expressed numerically. It is instead expressed using measures like the variance, standard deviation or coefficient of variation, depending on the conditions of measurement.

  • Measurement conditions
    Variability between replicate measurements can be caused by many factors, including the operator, the calibration of the equipment and the environment.
  • Variance parts
    Variance components are an estimate of the portion of total variability that is accounted for by a specific source of variability.
  • Precision profile plot
    A precision profile plot displays precision relative to the measured quantity value for the measurement interval.
  • Variance operation
    A variance function is a relationship between the measured quantity value and the variance.

Measurement Systems Analysis (MSA), is a tool that analyzes the variation in every type of inspection, measurement and test equipment. It’s the system that assesses the quality of the measurement system. It allows us to ensure that our measurement results are consistent with our process.

Six Sigma is a system that measures everything. Measurement System Analysis (MSA), an experimental and mathematical way to determine how much variation within the measurement process contributes towards overall process variability.

What Precision in Measurement Data?

Measurement data refers to a set of tools or methods that are used to measure the objects.

DMAIC is a tool to remove errors from our processes – and in particular, it limits variation. You can also find the total observed variation in two flavors:

Total Variation = Measurement Variation + Process Variation

Let’s take, for example, the number of cups of M&Ms in a production run. You will get different measurements if you use a measuring cup that is inaccurate and your colleague uses a more accurate measuring device. The measurement variation is the sum of all the variations between your measuring cups.