Konfidensnivå

Konfidensnivå, often translated as confidence level, is a fundamental concept in statistical inference. It quantifies the uncertainty associated with a statistical estimate, such as a confidence interval. A specific confidence level, commonly expressed as a percentage (e.g., 95%), indicates the proportion of times that an interval constructed using a particular method would contain the true population parameter if the same study were repeated many times.

For instance, a 95% confidence interval means that if we were to draw an infinite number of samples and construct a confidence interval for each, approximately 95% of those intervals would capture the true population mean. It is crucial to understand that the confidence level does not refer to the probability that a specific interval contains the true parameter. Once an interval is calculated from a sample, the true parameter is either in that interval or it is not; there is no probability associated with it.

The choice of confidence level is a trade-off between precision and certainty. A higher confidence level, such as 99%, will generally result in a wider interval, providing more certainty but less precision about the parameter's value. Conversely, a lower confidence level, like 90%, yields a narrower interval, offering more precision but with less certainty. Common confidence levels in practice are 90%, 95%, and 99%. The calculation of a confidence interval typically involves a point estimate, a margin of error, and the chosen confidence level.