2.4. Calculation of Trueness and Precision

Trueness and precision were quantified in terms of the relative error. ∆d_M represents the trueness of the test results. The smaller the value of ∆d_M, the higher the trueness of the scanner. ∆S(d_M) represents the precision of the test results. The smaller the ∆S(d_M), the higher is the precision of the scanner.

Calculate the relative error according to Equations (1) and (2). [30].

d _R represents the reference value of the sample, and d_M represents the measured value (including length, depth, height, and distance from the center).

S represents the standard deviation and d_R represents the reference value of the sample.

The ANSI/ADA No. 132 professional standard considers the relative error of the indexes in samples 1 and 2. Less than 0.01 mm is the acceptable range in the dental requirements category, and a relative error of less than 0.0025 mm represents the distance between sphere reference points to ensure that the acceptable threshold value in the dental requirements category is used as the threshold value.