Fisher FERITSCOPE FMP30 - Page 225

Page 220 Operator‘s Manual FERITSCOPE
®
FMP30
Glossary
standard deviations can still have the same mean value.
Figure 16.8: Measurement series with the same mean value but different standard devia-
tion
s.
Standard deviation of the readings that have been taken using a fixed
block size.
where:s. = mean standard deviation of the block standard deviations
N
Bl
= number of evaluated blocks
s
j
= standard deviation of the readings of a block
sa
Calculated by the FERITSCOPE
®
FMP30 only when the measurements
were performed with fixed block size and the deviations of the block
mean values cannot be attributed to the deviations within the subgroups,
as determined by analysis of variance methods (C.O.V.). It describes
the deviations of the block mean values in relation to the deviations of
the single measurements within the blocks. With a suitable measurement
strategy, sa is a measure of the product deviation
where:sa = deviation of the block mean values corrected with regard to the deviation
of the single readings
sII sII
N
j
= block size (number of readings per block)
= estimated value for the standard deviation
 of the population
s.
1
N
Bl
--------- s
j
j1=
N
Bl

=
sa
s
2
II

ˆ
2
–
N
j
--------------------=

ˆ