The purpose of the population and computing a statistic, such as the data, to approximate, is the population. The sample statistic estimates the underlying population value is always an issue. The confidence interval addresses this issue because it provides a range of values which is likely to contain the population of interest.
Confident level such as 95%, selected by the uses. It means that if the same population is sampled on numerous occasions and the resulting intervals would bracket the true population in approximately 95% of the cases. The one and two-sided confidence intervals can be one or two-sided. It brackets the population parameter from above and below.
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