Confidence Interval Calculator
Use this Confidence Interval Calculator to calculate confidence intervals, margin of error, and confidence level from sample data quickly and accurately.
A Confidence Interval Calculator is a statistical tool used to estimate a range of values within which a population parameter is likely to fall, based on sample data. Instead of providing a single estimate, confidence intervals give a lower and upper bound along with a confidence level, commonly 90%, 95%, or 99%.
Confidence intervals are widely used in statistics, research, surveys, data analysis, and quality control. They help quantify uncertainty and provide a clearer understanding of how reliable a sample estimate is when applied to a larger population.
The most common confidence interval formulas are:
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Confidence Interval = Sample Mean ± Margin of Error
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Margin of Error = Critical Value × (Standard Deviation ÷ √Sample Size)
This Confidence Interval Calculator allows users to calculate intervals for both population means and population proportions. Depending on the data type and sample size, the calculator applies either a Z-score or a T-score to ensure accurate statistical results.
By using this calculator, you can:
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Estimate population parameters from sample data
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Calculate margin of error precisely
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Compare confidence levels and their impact on interval width
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Improve decision-making in statistical analysis
Whether you are a student, researcher, analyst, or professional working with data, confidence intervals are essential for interpreting results with statistical confidence.
FAQ
What does a confidence interval tell you?
A confidence interval shows the range in which a population parameter is likely to fall at a given confidence level.
What is the difference between Z-score and T-score?
Z-scores are used when population standard deviation is known or sample size is large, while T-scores are used for smaller samples with unknown population standard deviation.
What confidence level should I use?
Common confidence levels are 90%, 95%, and 99%. Higher confidence levels produce wider intervals.
What is margin of error?
Margin of error represents the maximum expected difference between the sample estimate and the true population value.
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