1. What is ICC?

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

2. How Does the Calculator Work?

The calculator uses the basic ICC formula:

Where:

• Variance Between Subjects — Variability due to actual differences between subjects
• Variance Within Subjects — Variability due to measurement error or other within-subject factors

3. Importance of ICC

Details: ICC is widely used in research to assess measurement reliability, inter-rater reliability, and test-retest reliability. It's particularly important in fields like psychology, medicine, and behavioral sciences.

4. Using the Calculator

Tips: Enter the between-subjects and within-subjects variance values (must be ≥0). The calculator will compute the ICC value which ranges from 0 (no reliability) to 1 (perfect reliability).

5. Frequently Asked Questions (FAQ)

Q1: What is a good ICC value?
A: Generally, ICC > 0.75 indicates excellent reliability, 0.60-0.74 good, 0.40-0.59 fair, and <0.40 poor reliability.

Q2: What's the difference between ICC and Pearson's r?
A: ICC accounts for systematic differences between measurements, while Pearson's r only measures linear correlation.

Q3: Are there different types of ICC?
A: Yes, there are different ICC models (one-way, two-way) and types (absolute agreement vs. consistency).

Q4: When should I use ICC versus Cronbach's alpha?
A: Use ICC for test-retest or inter-rater reliability, and Cronbach's alpha for internal consistency of multi-item scales.

Q5: Can ICC be negative?
A: No, ICC ranges from 0 to 1. Negative values would indicate calculation errors.