As a domain expert in statistics and data analysis, I can provide a detailed explanation of the concept of "confidence level" in statistical terms. Confidence level is a fundamental concept in inferential statistics, which is the branch of statistics that deals with drawing conclusions from data.

In statistics, we often deal with samples to make inferences about the entire population. The confidence level is a measure of how likely it is that the results from a sample accurately represent the population. It is expressed as a percentage and it's used to construct a confidence interval around a sample statistic, which is an estimate of a population parameter.

The confidence interval is a range that includes the true population parameter with a certain level of confidence. For example, if we say we are 95% confident, it means that if we were to take many samples and construct a confidence interval from each, then 95% of those intervals would contain the true population parameter.

Let's consider a simple example. Suppose we want to know the average height of all adults in a country. It's impractical to measure every adult, so we take a sample of adults and calculate the average height of that sample. The sample mean is our best guess for the population mean. However, because we only measured a sample, there's some uncertainty. The confidence level tells us how confident we can be that our sample mean is close to the true population mean.

The 95% confidence level is the most commonly used because it provides a good balance between precision and the width of the confidence interval. It means that if we were to repeat the sampling process many times, 95% of the confidence intervals we calculate would contain the true population mean.

On the other hand, a 99% confidence level indicates a higher level of confidence, but it also means that the confidence interval will be wider, which can make the estimate less precise. This level is used when a higher degree of certainty is required.

It's important to note that a confidence level does not mean that the population parameter falls within the interval 95% or 99% of the time in a single sample. Instead, it refers to the long-run frequency with which the confidence interval would contain the population parameter if the sampling process were repeated an infinite number of times.

In summary, the confidence level is a critical concept in statistics that helps us quantify the uncertainty associated with estimates made from sample data. It's a tool that allows us to make informed decisions based on the data we have, while acknowledging the inherent variability and uncertainty in those data.

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It is expressed as a percentage and represents how often the true percentage of the population who would pick an answer lies within the confidence interval. The 95% confidence level means you can be 95% certain; the 99% confidence level means you can be 99% certain. Most researchers use the 95% confidence level.read more >>