Title: Confidence Interval Calculator
Headings: Confidence Interval Calculator
Confidence Interval Calculator
What is the confidence interval?
Calculating confidence intervals:
Z-values for Confidence Intervals

Content: Confidence Interval Calculator
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Confidence Interval Calculator
Use this calculator to compute the confidence interval or margin of error assuming the sample mean most likely follows a normal distribution. Use the Standard Deviation Calculator if you have raw data only. What is the confidence interval? In statistics, a confidence interval is a range of values that is determined through use of observed data, calculated at a desired confidence level, that may contain the true value of the parameter being studied. The confidence level, for example, a 95% confidence level, relates to how reliable the estimation procedure is, not the degree of certainty that the computed confidence interval contains the true value of the parameter being studied. The desired confidence level is chosen prior to the computation of the confidence interval and indicates the proportion of confidence intervals, that when constructed given the chosen confidence level over an infinite number of independent trials, will contain the true value of the parameter. Confidence intervals are typically written as (some value) ± (a range). The range can be written as an actual value or a percentage. It can also be written as simply the range of values. For example, the following are all equivalent confidence intervals: