Documentation/How Tos/Calc: CONFIDENCE function

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See also (in the Array Function category); GROWTH, LINEST, LOGEST, TREND

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CONFIDENCE

Returns a confidence interval.

Syntax:

CONFIDENCE(α; sd; size)

sd (> 0) is the (known) standard deviation of a normal distribution.

size is the size of a sample from that distribution.

α is the significance level (0 < α < 1), which determines the desired confidence level = (1 - α)*100%. Thus for example α = 0.05 gives a 95% confidence level.

CONFIDENCE returns a value that when added and subtracted from the sample mean gives an interval within which the population mean is expected to lie with the specified confidence level.

CONFIDENCE calculates NORMINV(1 - α/2; 0; 1) * sd / √(size)

Example:

CONFIDENCE(0.05;1;20)

returns approximately 0.438. With a 95% confidence level, the mean of the entire population lies within ±0.438 of the sample mean.

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See Also

• NORMDIST
• NORMINV

• Statistical functions

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