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Chapter 2

Aggregate functions 29

Description

Returns the variance of a population represented by a series of non-blank values. The

variance of a population distribution is a measure of how spread out the distribution is.

Use this function on any of the following fields:

• a repeating field (repeatingField).

• a field in matching related records specified by (table::field), whether or not

these records appear in a portal.

• several non-repeating fields in a record (field1;field2;field3...).

• corresponding repetitions of repeating fields in a record

(repeatingField1;repeatingField2;repeatingField3), if the result is

returned in a repeating field with at least the same number of repeats.

• several fields in the first matching record specified by

(table::field1;table::field2;...). You can include fields from different

tables (table 1::field A;table 2::field B...).

Examples

A portal displays the related values 5, 6, 7, and 8 in Scores.

VarianceP(table::Scores) returns 1.25.

In the following examples:

• Field1 contains two repetitions with values of 1 and 2.

• Field2 contains four repetitions with values of 5, 6, 7, and 8.

• Field3 contains four repetitions with values of 6, 0, 4, and 4.

• Field4 contains one repetition with a value of 3.

VarianceP(Field4) results in an error since the variance of a single value is not

defined.

VarianceP(Field1;Field2;Field3) returns 4.66666666..., 6.22222222..., 2.25, 4

if the calculation is a repeating field.

Student example:

Two classes of students take an exam. Class 1 has scores of 70, 71, 70, 74, 75, 73, 72

and Class 2 has scores of 55, 80, 75, 40, 65, 50, 95. The population variance for each

class is:

Class 1: 3.26530612...

Class 2: 310.20408163...

The population variance for Class 1 is much lower than the population variance for Class

2 because the scores for Class 1 are more tightly clustered.

VarianceP

… x

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… x

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–=

1 2 ... 24 25 26 27 28 29 30 31 32 33 34 ... 237 238

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Filemaker TH325Z/A Fiche technique Page 29

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