1. What is Intraclass Correlation?

Intraclass Correlation Coefficient (ICC) is a measure of reliability or agreement among different measurements of the same subject. It ranges from 0 to 1, with higher values indicating greater reliability.

2. How Does the Calculator Work?

The calculator uses the ICC formula:

Where:

• \( \text{variance\_subjects} \) — Variance between subjects
• \( \text{variance\_error} \) — Variance due to measurement error

Explanation: The ICC represents the proportion of total variance that is due to differences between subjects.

3. Importance of ICC Calculation

Details: ICC is crucial for assessing measurement reliability in research, clinical assessments, and psychological testing. It helps determine if measurements are consistent across different raters or time points.

4. Using the Calculator

Tips: Enter the variance between subjects and the error variance (both must be ≥0). The calculator will compute the ICC value between 0 and 1.

5. Frequently Asked Questions (FAQ)

Q1: What does an ICC value of 0.8 mean?
A: An ICC of 0.8 indicates excellent reliability, meaning 80% of the variance is due to true differences between subjects.

Q2: What are acceptable ICC values?
A: Generally: <0.5=poor, 0.5-0.75=moderate, 0.75-0.9=good, >0.9=excellent reliability.

Q3: How is ICC different from Pearson correlation?
A: ICC assesses absolute agreement, while Pearson correlation assesses relative agreement (linear relationship).

Q4: What are common uses of ICC?
A: Test-retest reliability, inter-rater reliability, and assessing consistency of measurement tools.

Q5: Can ICC be negative?
A: No, ICC ranges from 0 to 1 as it's a ratio of variances (which are always positive).