Confidence Interval

In a confidence interval, it is estimated that a population parameter has a certain probability, generally 90%, 95% or 99%.

The confidence limits are the two extreme values of the confidence interval which define the range.


Confidence Level

The confidence level is the probability that the parameter estimate is within the confidence interval. It is represented by (1 − α), where α is the significance level.

Critical Values

A critical value is the value corresponding to a given significance level.

1 − α α/2 zα/2
0.90 0.05 1.645
0.95 0.025 1.96
0.99 0.005 2.575

α/2 = 0.05 1 − α = 0.90

Confidence Interval Graph


Confidence Interval Operations

α/2 = 0.0251 − α = 0.95

Confidence Interval Graph


Confidence Interval Solutions


α/2 = 0.0051 − α = 0.99

Confidence Interval Graph


Confidence Interval Solution