The four keys to achieve reliable test results

There are four components to the achievement of reliable test results: accuracy, repeatability, reproducibility, and traceability.

 To provide a complete view of the underlying concept of reliable test results, we offer here an overview of key terminology and corresponding practical examples.  You can also view our video on YouTube or visit our website to learn more.

Measurements that are true and precise are accurate.  Trueness describes the closeness of agreement between a reference value and the average of individual test results.  Precision is the closeness of agreement between individual test results obtained under stipulated conditions, however, this still does not mean that the values obtained by measurement are also true.  They can be precisely untrue, for example, due to systematic error. 

Accuracy Examples:  
Tensile modulus measurements on plastics require the use of high-accuracy contact- or non-contact extensometers.  Those must be able to sense deformations below one micron.  
Periodic calibrations in accordance with industry regulations and standards establish the difference between set value and actual value. This involves comparing the components of the measurement chain of a testing machine with a national or reference measurement standard.  Zwick USA is A2LA accredited to provide a robust suite of calibration services.
In the case of applications involving brittle specimens, or in creep and fatigue tests, the exact alignment of the load train is critical to obtaining accurate test results.  Periodic alignment verification services assess the alignment of the load train and support accuracy in measurement.

To demonstrate precision under repeat conditions, specifically; the same measurement procedure, the same operator, the same measuring equipment, the same location, and the same test conditions. 

Repeatability Examples: 
Automated testing — starting from specimen identification, cross-section measurement, uniform insertion and alignment, up to data handling — creates the highest possible repeatability of test results. 
The System Configuration Builder in our testXpert III testing software saves all relevant machine settings and assigns them to a user-defined test environment.  This guarantees an identical test configuration every time, enabling optimum test result repeatability. 

To demonstrate precision when the same standard or test procedure is performed using similar measuring equipment — generally at different locations, with multiple operators and test conditions.

Reproducibility Examples: 
Our testXpert testing software includes more than 600 standard-compliant, pre-configured standard test programs, ensuring reproducibility.  All parameters, results, and test reports are pre-configured in accordance with the relevant standard and use the terminology of the relevant industry.

The full and complete documentation of a measured result.  Inputs gathered include information on who, how, when, and where the test result was determined.

Traceability Examples: 
Traceability of data is achieved by using electronic logging and documentation of all processes and events on the testing machine.  This is accompanied by an accurate time-stamp, which is assigned to the operator.  Intelligent user management controls all access rights and safeguards data against manipulation. 

Click here for further information on the concept of reliable test results and its associated benefits for your testing program. 

View the overview video on the ZwickRoellTV YouTube channel. 


Zwick Roell Testing Machines Pvt. Ltd
Tel.  +91 44 43090450
E-Mail  info@zwick.co.in


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