Quantcast Random Sampling - mo3270100

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the contractor's price is contrary to NAVFACENGCOM policy. This is because
neither the size of the sample nor the method of sample selection are in
accordance with the rules for statistical sampling techniques. As a result,
the extrapolation of planned sampling has no validity and the ODR may not be
compared with the MADR, being defined as the defect rate in the
population above which the contractor's quality control is considered
unsatisfactory.
Changes in the DR from month to month, calculated on the basis of the total
population, gives an indication of whether the contractor's quality control
is getting better or worse.
An alternate approach is to specify the MADR as a number of defects rather
than as a percentage when planned sampling method of
surveillance (e.g., 10 defects rather than 2% per surveillance period).
This alternate approach still does not permit extrapolation of the total
number of defects in the entire population of services as is done in random
sampling.
4-740 Random Sampling.  When random sampling for extrapolated deductions
(RSED), or random sampling without extrapolated deductions (RSWED) is used,
the procedures are outlined in the surveillance guide as follows:
(a) Contract Requirement. List the contract requirements together with
work requirements and standards of performance from the expanded performance
requirements summary (PRS), see Figure 4-1.
(b) Primary Method of Surveillance. The primary method of surveillance
is random sampling. Validated customer complaints are a good supportive
surveillance method.
(c) MADR.  The maximum allowable defect rate (MADR) isspecified in the
PRS.  The MADR is the defect rate in the population above which the
contractor's quality control is considered unsatisfactory. MADR is stated
as a percentage.
(d) Identification of the population. The total number of work
occurrences for a given function that are to be performed during the
surveillance period must be known or accurately estimated as shown at
4-510.  If the work is being carried out at several locations, the work
locations are numbered sequentially in the order corresponding to the most
efficient route the QAE would follow if all the locations were inspected .
(See 4-520 Sequential Numbering of Work Locations.)
(e) Sequential Numbering of the Population. Once the population has
been identified, the individual services in the population must be assigned
sequential numbers so that each service in the population can be distinctly
identified from the rest of the population as shown at 4-600.
(1) Scheduled services. When work is scheduled, population size
is based on the monthly calendar as shown at 4-620. The population normally
will be different for each month.
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