# 90%, 95%, 99% Confidence Intervals

- 90% Confidence Interval = xbar ± 1.645(s/√n)
- 95% Confidence Interval = xbar ± 1.96(s/√n)
- 99% Confidence Interval = xbar ± 2.58(s/√n)

xbar = arithmetic mean

s = standard deviation

n = sample size

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They still expect you to remember this on Level 2.