Brian Dunning's FileMaker Custom Functions

CI95 ( AllData )

CONFIDENCE INTERVAL CALCULATION (95%) = IC95

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Paolo Marchetto   Paolo Marchetto - Show more from this author
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  Sample input:
PAS = 100, 102, 105, 99, 101, 105, 107, 112, 131, 92, 124
  Sample output:
CI95% = 99.4-114.7

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

CONFIDENCE INTERVAL CALCULATION (95%) = CI95

CI95 (of an mean) = Mean( AllData ) +/- t * STDerr

Where:

STDerr is the standard error;

The standard error of a mean is obtained by dividing the standard deviation by the square root of the sample's (AllData) numerosity (n).

AllData is the content of a multiple field or the content of a field read via a one-to-many relationship.

t is a coefficient derived from the "Table of t-values for Student's distribution" (here it's predetermined from a simplified table). You must take into account that the degrees of freedom in Italian 'Gradi Di Libertà' (GDL) are calculated as follow: AllData size - 1.

 

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