Statistical Terms; Storage Capacity Overflow - Extech Instruments CG304 User Manual

Statistical Analysis Considerations
The meter calculates statistics from a maximum of 80 readings (For Group 1 through Group 4, a
maximum of 400 readings can be stored). Note that readings cannot be stored when in DIRECT
mode. However, statistics on these readings can still be calculated. When the meter is powered
off or if the working mode is changed (in the programming menu), the DIRECT mode statistics
will be lost. The following statistical values can be calculated:
 NO.: Number of readings
 AVG: Average value
 Sdev. : Standard deviation (square root of a data set's variance)
 MAX: Maximum reading
 MIN: Minimum reading
Statistical Terms
Average value (


x x /
Standard Deviation (Sdev)
The sample standard deviation is a statistic that measures how the sample value is
distributed around the sample mean. The standard deviation of a set of numbers is the root
mean square of the variance S
The variance of a list is the square of the standard deviation of the list, that is, the average of
the squares of the deviations of the numbers in the list from their mean divided by
the(number of readings ‐1 )
2
Variance: S =
Standard deviation: S=
NOTE:
Use the DELETE parameter from the programming menu immediately after an outlier or
erratic reading has been taken. Refer to the Delete function in Programming Menu.
Storage Capacity Overflow
In GROUP mode, if the storage capacity is exceeded, statistics will not be updated, although
measurements can still be made. If the memory is full, subsequent readings will not be
included in the statistics. The meter's display will show "FULL" (in the SINGLE measurement
mode).
In DIRECT mode, when the memory is full, the newest reading will replace the oldest reading
and the statistics will be updated.
x
) is the sum of readings divided by the number of readings.
n
2

2

( x x )
2
S

/( n ) 1
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