Confidence Interval Calculator

Calculate precise statistical intervals for population means and proportions

About Confidence Interval Calculator

A confidence interval is a range of values that's likely to include a population parameter with a certain degree of confidence. Our calculator helps you determine this range for population means and proportions, which is essential for statistical analysis and research.

Key Features:

  • Calculate confidence intervals for both means and proportions
  • Multiple confidence level options (90%, 95%, 99%)
  • Different calculation methods for proportions
  • Visual representation of the confidence interval
  • Detailed calculation steps and formulas
  • Mobile-friendly responsive design

Common Applications:

  • Academic research and statistical analysis
  • Market research and survey analysis
  • Quality control and process improvement
  • Medical and scientific studies
  • Business decision making

Formulas Used:

For Means:

CI = x̄ ± t*(s/√n)
Where:
x̄ = sample mean
t* = critical t-value
s = sample standard deviation
n = sample size

For Proportions (Normal Approximation):

CI = p̂ ± z*√(p̂(1-p̂)/n)
Where:
p̂ = sample proportion
z* = critical z-value
n = sample size