Agilent Technologies Infiniium 8000A Programmer's Reference Manual page 554

Query
Returned Format
<value> The percentage of points within three standard deviations of the mean of the
<result_state> If SENDVALID is ON, the result state is returned with the measurement result.
Example
Measure Commands
HISTogram:M3S
:MEASure:HISTogram:M3S? [<source>]
The :MEASure:HISTogram:M3S? query returns the measurement of the
percentage of points within three standard deviations of the mean of the
histogram.
[:MEASure:HISTogram:M3S]<value>[,<result_state>]<NL>
histogram.
Refer to the MEASure:RESults command, for a list of the result states.
This example returns the percentage of points within three standard deviations
of the mean of the current histogram and prints the result to the computer's
screen.
10 OUTPUT 707;":SYSTEM:HEADER OFF"
20 OUTPUT 707;":MEASURE:HISTOGRAM:M3S? WMEMORY1"
30 ENTER 707;Histm3s
40 PRINT Histm3s
50 END
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