# Confidence Interval Calculator

> Calculate a two-sided normal confidence interval and margin of error for a population mean.

Page: https://askcalculators.com/calculator/confidence-interval-calculator/
Definition: https://askcalculators.com/calculator/confidence-interval-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/confidence-interval-calculator/schema.json
Version: 2.0.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/confidence-interval-calculator/?sampleSize=100&sampleMean=50&standardDeviation=10&confidenceLevel=95

## Inputs
- sampleSize: Sample size (n); type=number; required; default=100; min=1; max=1000000000
- sampleMean: Sample mean (x̄); type=number; required; default=50
- standardDeviation: Standard deviation (σ or s); type=number; required; default=10; min=0
- confidenceLevel: Confidence level; type=select; required; default=95; values=80|85|90|95|98|99|99.9

## Outputs
- lowerBound: Lower bound; format=number; primary
- upperBound: Upper bound; format=number; primary
- interval: Confidence interval; format=text
- marginOfError: Margin of error; format=number
- standardError: Standard error; format=number
- criticalZ: Critical z-score; format=number

## Formula
CI=x̄±z*·σ/√n; margin of error=z*·σ/√n.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.