# What is 95% confidence interval

This post is part of 'Statistics | General' series

A 95% confidence interval is a range of values that is likely to contain the true value of a population parameter with 95% probability.

To give an example, let's say you are interested in estimating the average height of all people in a certain town. You take a sample of 100 people from the town and find that the average height in the sample is 170 cm, with a 95% confidence interval of 165 cm to 175 cm. This means that if you were to take many different samples of 100 people from the town and calculate a 95% confidence interval for each sample, about 95% of those intervals would contain the true average height of all people in the town.

In other words, a 95% confidence interval provides a range of values that is likely to include the true population parameter. The wider the interval, the less precise the estimate, and the less confident we are that the interval contains the true value. Similarly, the narrower the interval, the more precise the estimate, and the more confident we are that the interval contains the true value.

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