Dranetz Guide Uživatelská příručka stáhnout pdf (Strana 218)

218

Dran-View 6 User Guide

19.2. Weighted Statistics

The samples inside the current time limits are sorted in ascending sample

magnitude order along with their associated durations. A given sample is assumed

to be the best estimate of line conditions until a new sample comes along to replace

it. Therefore its duration (or weighting) is given as the time difference between the

sample and the next sample. Starting at the lowest sample magnitude the associated

sample durations are summed. When the duration sum equals or exceeds the

desired percentage of the total duration of all samples, the magnitude is extracted

and shown. These are the values used for the median and percentage value

estimates.

We can think of the result as:

For N% of the time the values are less than or equal to the N% value. For the rest of

the time it is greater.

The weighted standard deviation is carried out using the following formulas. D

denotes durations and X denotes sample magnitudes:

Duration of all samples = D

total

Where D

is equal to the time duration associated with each individual sample.

Weighted (by duration) Average of Samples =

weighted

Using the weighted average as our model the formula for the weighted standard

deviation is as follows:

Weighted (by duration) Standard Deviation (biased) =

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Dranetz Guide Uživatelská příručka Strana 218