Confidence interval
A confidence interval is an interval of values made by a sample where the population parameter belongs with a certain probability. The probability is called the confidence level. A confidence interval is made by the standardized normal distribution, using the central limit theorem.
Example. A 95% confidence interval means an interval where the population parameter will be found with 95% certainty, we have 95% confidence that the interval contains the true population parameter.
Formulas for confidence interval for large samples: