What does a 95% confidence interval mean?

A 95% confidence interval means that if you repeated your study many times, about 95% of the calculated intervals would contain the true population parameter. It doesn't mean there's a 95% chance the true value is in your specific interval.

How do I choose the right confidence level?

95% is most common in research. Use 99% for more critical decisions (wider interval, more conservative). Use 90% when you can accept more risk (narrower interval, less conservative). Higher confidence levels require larger margins of error.

What's the difference between confidence intervals for means and proportions?

Mean intervals estimate the average value of a continuous variable. Proportion intervals estimate the percentage of a population with a certain characteristic. They use different formulas and assumptions.

How can I make my confidence interval narrower?

Increase your sample size, reduce variability in your data (better measurement techniques), or accept a lower confidence level. Sample size has the biggest practical impact on interval width.

Confidence Interval Calculator – Statistical Intervals

Calculate confidence intervals for means and proportions. Determine margin of error and statistical significance for survey and research data.

Confidence Interval Calculator – Statistical Intervals

Calculate confidence intervals for means and proportions. Determine margin of error and statistical significance for survey and research data.

Data Type*

Type of data you're analyzing

Sample Mean

Sample mean value (for mean calculations)

Sample Size (n)*

Number of observations in the sample

Standard Deviation

Sample or population standard deviation

Sample Proportion

Sample proportion (between 0 and 1)

Confidence Level*

Desired confidence level

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Math visualization will appear here

Understanding Confidence Intervals

A confidence interval provides a range of values that likely contains the true population parameter. It quantifies the uncertainty in your sample estimate and helps you understand the precision of your results.

Interpreting Confidence Intervals

Key concepts:

Confidence Level: Probability that the interval contains the true parameter
Margin of Error: Half the width of the confidence interval
Wider intervals indicate more uncertainty
Larger samples generally produce narrower intervals
Higher confidence levels produce wider intervals

How to Use This Calculator

Follow these simple steps to get accurate results:

Enter your data type
Enter your sample mean
Enter your sample size (n)
Enter your standard deviation
Enter your sample proportion
Enter your confidence level
Click the "Calculate" button to see your results
Review the detailed breakdown and explanation

Why Use Our Confidence Interval Calculator – Statistical Intervals?

100% free and no registration required
Instant, accurate calculations with professional formulas
Mobile-friendly design that works on any device
Privacy-focused - your data never leaves your browser
Educational content to help you understand the results

Frequently Asked Questions

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