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Confidence Interval Calculator

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How it works

For means: CI = x̄ ± z × (σ/√n). Use z=1.96 for 95% confidence, 2.576 for 99%. When σ is unknown and n < 30, use the t-distribution instead. For proportions: CI = p̂ ± z × √(p̂(1−p̂)/n). A 95% CI means if the experiment were repeated 100 times, roughly 95 intervals would contain the true parameter—not that there's a 95% chance the true value is in this interval.

95% CI: [94.6323, 105.3677]

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