Difference between revisions of "Documentation/How Tos/Calc: CONFIDENCE function"
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: <tt>'''CONFIDENCE'''</tt> 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. | : <tt>'''CONFIDENCE'''</tt> 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. | ||
| − | : <tt>'''CONFIDENCE'''</tt> calculates <tt>'''NORMINV(1 - α/2 | + | : <tt>'''CONFIDENCE'''</tt> calculates <tt>'''NORMINV(1 - α/2; 0; 1) * sd / √(size)'''</tt> |
=== Example: === | === Example: === | ||
Revision as of 21:21, 28 April 2009
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.
