Updated · Methodology: named formula library
Confidence Interval Calculator
95% CI for a sample mean.
Mean: 6. Median: 6. Min: 1. Max: 10. Std dev: 3.
Why This Calculation Matters
The Confidence Interval Calculator gives you a fast, accurate answer for confidence interval, useful for homework, coursework, or inside a larger problem. The formula is shown below so you can see exactly what the tool is doing and verify it against a textbook or other reference.
How to Use This Calculator
- Enter your values in the input fields, each one has a label and help text explaining what to type.
- Results appear instantly as you type; there's no "calculate" button to press.
- Change any input to compare scenarios side by side.
All math happens in your browser. Nothing you type is sent to a server, saved, or shared.
How to Use
Enter values in the fields on the left. Results update as you type, no submit button needed.
Understanding Results
Each output shows the calculated figure plus a breakdown of contributing inputs. Compare scenarios by editing any value.
Accuracy Notes
Every Confidence Interval Calculator on CalcIntel uses a documented formula. Results are estimates, real outcomes depend on assumptions and market conditions not captured in a simplified calculation.
Formula
Population SD: σ = √(Σ(x − μ)² / N). Sample SD: s = √(Σ(x − x̄)² / (n − 1)). Sample SD uses n − 1 (Bessel's correction) to correct bias.
Worked Example
Sample dataset: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
- values
- 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
- Result
- Mean: 5.5, Median: 5.5, SD: 2.87
Mean = (1+2+...+10)/10 = 5.5. Median = (5+6)/2 = 5.5. Population SD ≈ 2.87.
When to Use This Calculator
- Check homework, textbook problems, or coursework answers.
- Explore how the result changes as you vary inputs, great for intuition building.
- Verify a calculation inside a larger engineering, research, or data workflow.
Limitations & Common Mistakes
- Results are only as accurate as the inputs, double-check rounding and units.
- Numeric precision is limited by JavaScript floating-point arithmetic.
Frequently Asked Questions
What does the Confidence Interval Calculator compute?
It computes the mean (average), median, min, max, count, sum, and standard deviation of any list of numbers you enter. Numbers can be separated by commas, spaces, or newlines.
What's the difference between mean and median?
Mean is the arithmetic average (sum / count). Median is the middle value when sorted. Median is more robust to outliers — for income data, real-estate prices, or any skewed distribution, the median is usually the more honest "typical value."
Should I use sample or population standard deviation?
This calculator uses population standard deviation (divides by N). For statistical inference where your data is a sample of a larger population, you'd want sample SD (divides by N−1, Bessel's correction). The difference is small for N > 30.
Can I use this for grades/scores?
Yes — for class grades, test scores, or any list of numerical observations. For weighted averages (e.g., GPA where credit hours matter), use the GPA Calculator instead.
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Source: BLS Consumer Price Index, 2026.