Krautkramer DynaPOCKET - Information about the Statistical Evaluation

7-8 Issue 03, 04/2005 Krautkramer DynaPOCKET
The rebound hardness testing method Information about the statistical evaluation
7.4 Information about the
statistical evaluation
With a corresponding setting, the DynaPOCKET dis-
plays the statistical average ( x¯ ).
Every measurement is subject to a measurement un-
certainty. In this connection, the measuring errors con-
sist of the following single errors:
❚ the basic measurement inaccuracy of the method of
measurement used,
❚ the handling of the probes,
❚ the preparation of the material to be measured
(surface or heat treatment),
❚ the homogeneity of the material to be measured,
❚ external influences (contamination, humidity, tem-
perature).
The statistiscal evaluation is intended to help you to
better assess your measurements and to make more
reliable decisions on the quality of the material under
test.
The average of a measurement set is the more accu-
rate, the more single measurements you carry out. At
the same time, however, many single measurements
mean that more “outliers” are included. For this reason,
the difference between minimum value and maximum
value is no reliable yardstick for the evaluation of a
measurement set containing more than around 12 mea-
suring points.
The average ( x¯ ) is arithmetically calculated:
with
x¯ = Average
x = Single measurement
n = Number of measurements
x¯ =
(x
1
+ x
2
+ x
3
+ ... + x
n
)
n