Related Experiment Video
Updated: May 1, 2026

Subjective Refraction Test Using a Smartphone for Vision Screening
Published on: October 18, 2024
Concurrent validity and reliability of the Simple Goniometer iPhone app compared with the Universal Goniometer
Anne Jones1, Rebecca Sealey, Michael Crowe
1Department of Physiotherapy, James Cook University , Townsville, Queensland , Australia .
Objectives:
The aim of this study was to assess the concurrent validity and reliability of the Simple Goniometer (SG) iPhone® app compared to the Universal Goniometer (UG).
Design:
Within subject comparison design comparing the UG with the SG app.
Setting:
James Cook University, Townsville, Queensland, Australia.
Participants:
Thirty-six volunteer participants, with a mean age of 60.6 years (SD 6.2).
Interventions:
Not applicable.
Main Outcome Measure:
Thirty-six participants performed three standing lunges during which the knee joint angle was measured with the SG app and the UG.
Results:
There were no significant differences in the measures of individual knee joint angles between the UG and the SG app. Pearson correlations of 0.96-0.98 and intraclass correlation coefficients of 0.97-0.99 (95% confidence interval: 0.95-1.00) were recorded for all measures. Using the Bland-Altman method, the standard error of the mean of the differences and the standard deviation of the mean of the differences were low.
Conclusion:
The measurements from the SG iPhone® app were reliable and possessed concurrent validity for this sample and protocol when compared to the UG.
Related Concept Videos
Uncertainty in Measurement: Reading Instruments
Gyroscope
Reliability and Validity
Calibration Curves: Correlation Coefficient

