The better way to determine the validity, reliability, objectivity and accuracy of measuring devices.
BACKGROUND
In relation to statistical analysis, studies to determine the validity, reliability, objectivity and precision of new measuring devices are usually incomplete, due in part to using only correlation coefficient and ignoring the data dispersion.


OBJECTIVE
The aim of this study was to demonstrate the best way to determine the validity, reliability, objectivity and accuracy of an electro-inclinometer or other measuring devices. Another purpose of this study is to answer the question of whether reliability and objectivity represent accuracy of measuring devices.


METHODS
The validity of an electro-inclinometer was examined by mechanical and geometric methods. The objectivity and reliability of the device was assessed by calculating Cronbach's alpha for repeated measurements by three raters and by measurements on the same person by mechanical goniometer and the electro-inclinometer. Measurements were performed on "hip flexion with the extended knee" and "shoulder abduction with the extended elbow." The raters measured every angle three times within an interval of two hours. The three-way ANOVA was used to determine accuracy.


RESULTS
The results of mechanical and geometric analysis showed that validity of the electro-inclinometer was 1.00 and level of error was less than one degree. Objectivity and reliability of electro-inclinometer was 0.999, while objectivity of mechanical goniometer was in the range of 0.802 to 0.966 and the reliability was 0.760 to 0.961. For hip flexion, the difference between raters in joints angle measurement by electro-inclinometer and mechanical goniometer was 1.74 and 16.33 degree (P<0.05), respectively. The differences for shoulder abduction measurement by electro-inclinometer and goniometer were 0.35 and 4.40 degree (P<0.05).


CONCLUSIONS
Although both the objectivity and reliability are acceptable, the results showed that measurement error was very high in the mechanical goniometer. Therefore, it can be concluded that objectivity and reliability alone cannot determine the accuracy of a device and it is preferable to use other statistical methods to compare and evaluate the accuracy of these two devices.
Department of Sports Sciences, School of Sports Sciences, University of Isfahan, Isfahan, Iran.
Parvin
P
Pazira
Department of Sports Sciences, School of Sports Sciences, University of Isfahan, Isfahan, Iran.
Mahdi
M
Rostami Haji-Abadi
Department of Sports Sciences, School of Sports Sciences, University of Isfahan, Isfahan, Iran.
Vahid
V
Zolaktaf
Department of Electrical Engineering, School of Engineering, University of Isfahan, Isfahan, Iran.
Mohammadfarzan
M
Sabahi
Department of Biomechanical Engineering, School of Mechanics, Iran University of Science and Technology, Tehran, Iran.
Toomaj
T
Pazira
D053587:Arthrometry, Articular / Q000295:instrumentation*; D004867:Equipment Design / Q000379:methods*; D006801:Humans; D016059:Range of Motion, Articular; D015203:Reproducibility of Results
Electro-goniometer; goniometry; psychometric properties