5.3 Performing Statistical Calculations on Measured Values
111
5
Statistical calculations can be performed on up to 30,000 measured values, with results dis-
played. Printing is also available (p. 245).
Calculation types: average, maximum and minimum values, population standard deviation,
sample standard deviation, process compatibility indices
Deleting Statistical Calculation Results
Stored data is automatically erased at the following times:
5.3 Performing Statistical Calculations on
Measured Values
Maximum value
Xmax = MAX (x
1
, ....., x
n
)
In these formulas, n represents the number
of valid data samples.
* Process capability index
• The process capability indices repre-
sent the quality achievement capability
created by a process, which is the
breadth of the dispersion and bias of
the process' quality. Generally,
depending on the values of Cp and
Cpk, process capability is evaluated as
follows:
Cp, Cpk >1.33............Process capabil-
ity is ideal
1.33 ≥ Cp, Cpk >1.00.Process capabil-
ity is adequate
1.00 ≥ Cp, Cpk ...........Process capabil-
ity is inadequate
•
UPP and LOW are the upper and
lower thresholds of the comparator.
• When the BIN function is on, the pro-
cess capability index will not be calcu-
lated.
Minimum value
Xmin = MIN (x
1
, ....., x
n
)
Average
Population
standard
deviation
Standard
deviation
of sample
Process
capability index
(dispersion) *
Process
capability
index (bias)*
σ
n
x
2
nx
2
–
n
---------------------------=
σ
n 1–
x
2
nx
2
–
n 1–
---------------------------
=
Cpk =
UPP−LOW UPP + LOW−2x
−
6σ
n−1
−
• When only one valid data sample exists, standard deviation of sample and process capa-
bility indices are not displayed.
• When σ
n-1
= 0, Cp and Cpk are 99.99.
• The upper limit of Cp and Cpk is 99.99. If Cp or Cpk exceeds 99.99, the value 99.99 is dis-
played
• Negative values of Cpk are handled as Cpk = 0.
• If statistical calculation is turned off and then back on without first clearing calculation
results, calculation resumes from the point when it was turned off.
• Measurement speed is restricted when statistical calculation is enabled.
• Turning on T or setting the measurement terminal to multiplexer automatically turns off
the statistical calculation function.
• when changing measurement conditions (low-power, measurement current, OVC,
100 M range high-precision mode, TC, non-offset scaling settings)
• when changing comparator settings (p.98)
• when changing BIN measurement function settings (p.108)
• when printing the statistical calculations (p. 245) (you can select whether to delete
results after printing (p.246))
• upon system reset (p. 134)
• when turning off the instrument
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