ClarityHow to use this tool
- Enter observed proportion, sample size, critical z value.
- Select Calculate to view the result.
- Check the method and assumptions below before using the result.
Input reference and sample values
Use the units and choices shown for each field. Sample values are provided for practice, not as recommendations.
| Input | Format and units | Sample |
|---|---|---|
| Observed proportion | Numeric value. Zero or positive. Maximum: 1. | 0.5 |
| Sample size | Whole numbers only. Minimum: 1. Maximum: 1000000. | 400 |
| Critical z value | Numeric value. Must be greater than zero. | 1.95996398 |
Result for these sample inputs
4.89990996 percentage points
Select Try the example in the form to load these values and calculate them again. This replaces the current form inputs. Compare the result with the method and worked explanation below.
The method, explained
Margin = z√[p(1 − p)/n], expressed in percentage points.
Using observed proportion = 0.5, sample size = 400, critical z value = 1.95996398454, the result is 4.89990996 percentage points. Change these example inputs to match your task; use the method above to check each step.
What to keep in mind
Normal approximation may be unreliable for small counts or proportions near zero or one. A descriptive or probability calculation under the stated assumptions. Check the sample design and model before interpreting results.
Methodology maintained by ClarityKit. How these tools are built and checked.