# What is meant by a 95% confidence interval?

Feb 19, 2018

A confidence interval is the probability that a value will fall between an upper and lower bound of a probability distribution.

#### Explanation:

An essential part of statistics is accounting for the variability of the estimate. Statistical analysis can also describe how far from the estimates the actual values are likely to be. To describe the precision of an estimate, statisticians use margins of error and confidence intervals.

The margin of error and the confidence interval apply to the estimated value of the parameter for the entire population, not for the value of the variable for particular individuals.

A confidence interval is an interval that will contain a population parameter a specified proportion of the time. The confidence interval can take any number of probabilities, with the most common being 95% or 99%.

For example: $\text{ }$ If repeated samples were taken and the 95% confidence interval computed for each sample, 95% of the intervals would contain the population mean. Naturally, 5% of the intervals would not contain the population mean.