This study aims to evaluate the validity and reliability of the Dr. Goniometer application for measuring elbow flexion by comparing it with a manual goniometer. Conducted at Beykent University, the study will include 60 participants without upper extremity issues. Measurements will be taken on the dominant arm using both a manual goniometer and Dr. Goniometer, each repeated twice. Dr. Goniometer measurements will be performed twice by two different evaluators. Validity will be assessed using the Pearson correlation coefficient, while reliability will be evaluated with ICC and SEM. Measurement differences will be analyzed using a paired t-test. The results will contribute to determining the clinical applicability of the Dr. Goniometer application.

This study is designed to assess both the validity and reliability of the Dr. Goniometer application for measuring elbow flexion. To do this, the study will compare the measurements taken using the Dr. Goniometer with those obtained using a manual goniometer, which is the standard tool typically used for such measurements.

Study Design and Participants:

The research will be conducted at Beykent University and will involve 60 participants. These individuals will be healthy and will not have any upper extremity issues (meaning they do not have any conditions affecting their arms).

The dominant arm of each participant will be used for measurement purposes. The dominant arm is the arm most commonly used for tasks like writing or eating.

Measurement Process:

Each participant's elbow flexion will be measured using both the manual goniometer and the Dr. Goniometer application.

The measurements will be taken twice using each tool, ensuring that there is a repetition for both the Dr. Goniometer and the manual goniometer.

Additionally, the Dr. Goniometer measurements will be performed twice by two different evaluators. This step is included to ensure that the measurements are consistent and to assess inter-rater reliability (the degree to which two different evaluators get the same results).

Statistical Analysis:

Validity will be assessed by calculating the Pearson correlation coefficient. This coefficient will measure the degree to which the measurements from the Dr. Goniometer correspond to the measurements from the manual goniometer. A high correlation would indicate that the Dr. Goniometer is valid and produces results similar to the established manual goniometer.

Reliability will be evaluated using two methods:

Intraclass Correlation Coefficient (ICC): This will assess the consistency or agreement of measurements taken with the same tool (e.g., using the Dr. Goniometer application multiple times by the same or different evaluators).

Standard Error of Measurement (SEM): This will measure the precision of the measurements and help understand the typical error expected in the measurements.

Measurement differences between the two tools (Dr. Goniometer and manual goniometer) will be analyzed using a paired t-test. This test will help determine whether there are any statistically significant differences between the measurements obtained from the two devices. If there is a significant difference, it could suggest that one tool is more accurate than the other or that they produce inconsistent results.

Expected Outcome:

The study will aim to determine whether the Dr. Goniometer application is clinically applicable. By assessing both its validity (how well it measures what it is intended to measure) and its reliability (how consistent and precise it is), the results will provide insight into whether this mobile application can be used effectively in clinical settings as a tool for measuring elbow flexion. If the application is found to be both valid and reliable, it could offer a convenient and accessible alternative to the traditional manual goniometer.

Inclusion Criteria:

• Aged between 18 and 65 years
• No history of musculoskeletal, neurological, or orthopedic conditions
• Voluntary participation

Exclusion Criteria:

• History of musculoskeletal, neurological, or orthopedic disorders affecting the upper extremity.
• Previous upper extremity trauma, surgery, or chronic pain limiting range of motion.
• Inability to provide informed consent or follow verbal instructions.

The study population consists of healthy adults aged 18-65 who have no history of musculoskeletal, neurological, or orthopedic disorders affecting the upper extremity. Participants will be recruited voluntarily from the general population and must be able to provide informed consent and follow verbal instructions.