Free Confidence Interval Calculator
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Confidence Interval Calculator

Easily Calculate Confidence Intervals for Your Data Instantly

Calculate confidence intervals with our free online statistical calculator. Perfect for research, data analysis, and determining margin of error with 90%, 95%, or 99% confidence levels.

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Calculate Confidence Interval

Enter your sample data to calculate confidence intervals and margin of error

How to Calculate Confidence Intervals

Follow these simple steps to calculate confidence intervals for your statistical data

1

Enter Sample Data

Input your sample mean, sample size, and standard deviation from your dataset.

2

Choose Confidence Level

Select 90%, 95%, or 99% confidence level based on your analysis requirements.

3

Get Interval Results

View the confidence interval bounds and margin of error for your data.

Calculator Features

Advanced statistical tools for accurate confidence interval calculations and analysis

Multiple Confidence Levels

Calculate intervals at 90%, 95%, and 99% confidence levels for different precision needs.

Margin of Error

Automatically calculate margin of error and understand the precision of your estimates.

Z-Score Integration

Built-in Z-score calculations for accurate statistical analysis and interpretation.

Secure Processing

All calculations performed securely in your browser with privacy protection.

Mobile Friendly

Works perfectly on all devices for statistical analysis anywhere.

Always Available

Free online tool available 24/7 with no registration required.

Confidence Level Comparison

Understanding different confidence levels and their applications in statistical analysis

Confidence LevelZ-ScoreInterpretationBest Used For
90%1.64590% chance interval contains true valuePreliminary analysis, quality control
95%1.9695% chance interval contains true valueGeneral research, standard analysis
99%2.57699% chance interval contains true valueMedical research, critical decisions

Frequently Asked Questions

Common questions about confidence intervals and statistical analysis

What is a confidence interval?

A confidence interval is a range of values that likely contains the true population parameter with a specified level of confidence (e.g., 95% confidence means we're 95% certain the true value lies within this range).

How do I interpret the confidence level?

The confidence level (90%, 95%, 99%) indicates how confident we are that the interval contains the true population parameter. Higher confidence levels create wider intervals.

What's the difference between margin of error and confidence interval?

The margin of error is the amount added and subtracted from the sample mean to create the confidence interval. The interval is mean ± margin of error.

When should I use different confidence levels?

Use 95% for most general purposes, 99% when you need higher certainty (medical research), and 90% when wider intervals are acceptable for preliminary analysis.

What sample size do I need for accurate results?

Generally, larger sample sizes (n > 30) provide more accurate confidence intervals. The larger the sample, the narrower and more precise the interval becomes.

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