Confidence Interval Calculator
Calculate confidence intervals for means, proportions, and differences
Mean CI
Proportion CI
Difference CI
Confidence Level
90%
z* = 1.645
95%
z* = 1.960
98%
z* = 2.326
99%
z* = 2.576
Confidence Interval for Mean
Confidence Interval Results
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Result description
Calculation Details
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Interpretation
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Confidence Interval Visualization
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Lower: 0
Estimate: 0
Upper: 0
Practical Examples
Example 1: Product Testing
A company tests 50 units of a new product and finds an average battery life of 120 hours with a standard deviation of 15 hours.
Example 2: Election Polling
A poll of 1000 voters shows that 45% support Candidate A. Calculate the confidence interval for the true proportion.
Multiple Calculators
Calculate CIs for means, proportions, and differences
Flexible Options
Choose from multiple confidence levels
Detailed Results
Get step-by-step calculations and interpretations
Visualization
Visual representation of confidence intervals
How to Use the Confidence Interval Calculator
- Select the type of confidence interval you need to calculate
- Choose your desired confidence level (90%, 95%, 98%, or 99%)
- Enter the required values in the input fields
- Click the calculate button to see your results
- View the detailed calculation explanation and interpretation
Confidence Interval Formulas
- Mean CI (σ known): x̄ ± z*(σ/√n)
- Mean CI (σ unknown): x̄ ± t*(s/√n)
- Proportion CI: p̂ ± z*√(p̂(1-p̂)/n)
- Difference of Means CI: (x̄₁ - x̄₂) ± z*√(σ₁²/n₁ + σ₂²/n₂)