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7.3.4 SST7 and SST10 => IC-Head on ICOS machines (analog Vision)
ASM AVS - USER MANUAL
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ASM AVS - USER MANUAL
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7.4 Notes on the statistics and on the interpretation of the results
7.4.1 Statistics
7.4.1.1 Statistical values
• Mean
Arithmetic mean of all the measured offsets.
• Standard deviation
The standard deviation or variance specifies the degree to which a random variable is distrib-
uted around the expected value.
The expected value is zero, as the expectation is that the machine works perfectly, i.e. with-
out any offset.
The value given in the view corresponds to the standard deviation with reference to 1σ (sig-
ma).
This means that if the result is to be evaluated with reference to the nominal values, the val-
ue must be multiplied by the sigma value of the nominal value (in the specification).
In the example above: Standard deviation for X axis = 15.18 µm => with reference to the
nominal values 15.18 *4 = 60.72 µm.
Therefore, to remain within the tolerance laid down in the specification of ±67 µm, a maxi-
mum deviation of the mean of all measured points of 6.28 µm is permitted.