I-CVI (Item-level Content Validity Index) is a validity metric that measures the proportion of experts who agree that a specific item on a measurement instrument is relevant and should be retained. Unlike CVR, I-CVI provides a straightforward probability-based measure ranging from 0 to 1.
I-CVI is particularly useful because it:
- Is easier to interpret than CVR (ranges from 0 to 1)
- Directly represents the proportion of expert agreement
- Has well-established evaluation criteria from multiple sources
- Works well with both small and large expert panels
I-CVI Formula
I-CVI = Number rating item as essential / Total number of experts
Interpretation
I-CVI directly represents the proportion of experts who rated the item as essential:
- I-CVI = 1.0: 100% of experts agree item is essential
- I-CVI = 0.8: 80% of experts agree item is essential
- I-CVI = 0.5: 50% of experts agree (no consensus)
- I-CVI = 0.0: 0% of experts agree (should definitely be removed)
Acceptable I-CVI Thresholds
Different evaluation criteria apply depending on the number of experts on your panel. The most commonly cited standards are from Lynn (1986) and Polit & Beck (2006):
| Experts | Criterion | Status | Action |
|---|---|---|---|
| 1-2 | I-CVI = 1.0 | Valid ✓ | Retain item |
| 3+ | I-CVI ≥ 0.78 | Valid ✓ | Retain item |
| 3+ | 0.70 to 0.78 | Questionable | Revise or gather more data |
| 3+ | I-CVI < 0.70 | Invalid | Remove or substantially revise |
Why These Thresholds?
With 1-2 experts, you need perfect agreement (1.0) because the expert panel is so small. With 3+ experts, 0.78 is considered the minimum threshold because this represents statistically significant agreement. The research shows that items rated essential by 78% of experts are consistently validated in later testing.
Practical Example
Example: Nursing competency scale
Situation: A nursing board develops a competency assessment with 5 experts reviewing a patient care item.
Ratings received:
- Expert 1: Essential
- Expert 2: Essential
- Expert 3: Useful but not essential
- Expert 4: Essential
- Expert 5: Essential
Calculation:
I-CVI = 4 / 5 = 0.80 ✓ Valid
Interpretation: With 5 experts and minimum threshold 0.78, this item's I-CVI of 0.80 is valid. The item should be retained.
I-CVI vs CVR
| Feature | I-CVI | CVR |
|---|---|---|
| Range | 0 to 1 | -1 to +1 |
| Interpretation | Proportion of experts | Proportion difference from chance |
| Ease of understanding | Very intuitive | Less intuitive |
| Threshold depends on | Number of experts | Number of experts |
| Best used when | You want simplicity | You want statistical rigor |
Common Mistakes to Avoid
- Forgetting to adjust threshold: Don't use 0.78 with 1-2 experts — use 1.0 instead
- Mixing rating systems: Ensure all experts use the same rating scale (1-3 or yes/no)
- Treating "Useful" as "Essential": Only count "Essential" ratings in the numerator
- Small expert panel: Using fewer than 3-5 experts reduces statistical power
References
Lynn, M. R. (1986). Determination and quantification of content validity. Nursing Research, 35(6), 382-385.
Polit, D. F., & Beck, C. T. (2006). The content validity index: Are you sure you know what's being reported? Research in Nursing & Health, 29(5), 489-497.