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 specify the MADR as a number of defects rather than as a percentage (e.g. 10
defects rather than 2%). The following example illustrates the computation.
CONTRACT REQUIREMENT: TAXI SERVICE
Sampling Method: Validated Customer Complaints.
Population: 523 trips in a month.
Number of (Customer Complaints: 22
Number of Validated Customer Complaints: 18
INSPECTION RESULTS:
MADR
QUALITY
VALIDATED
No. of
CONTROL
CUSTOMER
WORK
NUMBER
(Defects)
COMPLAINTS
RATING
DEFECTS
REQUIREMENT
UNSATISFACTORY
A. Response time 18
18
10
(d) Random Sampling. The defect rate is calculated by deducting an
adjustment factor shown in Appendix F, Table 3, from the observed defect
rate (ODR). The adjustment factor improves the statistical accura cy of the
results:
- Adjustment Factor
Defect rate =
number of defects
number of services sampled
The following example illustrates the computation.
CONTRACT REQUIREMENT: ROUTINE SERVICE CALLS
Sampling Method: Random Sampling.
Population: 600 Service Calls
Number of Services Sampled: 60
DEFECTS
IN
QC
DR** MADR
RATING
SAMPLE ODR
AF*
REQUIREMENT
3%
UNSAT
A. Response Time 6
10.00%
8.62%
1.38%
UNSAT
B. Classification 5
7.02%
3%
8.33%
1.31%
DEFECTS
QC
WORK
IN
DR** MADR
RATING
AF*
REQUIREMENT
SAMPLE ODR
UNSAT
3%
5.49%
1.17%
C. Cost accounting 4
6.66%
SAT
3%
0.90%
2.43%
D. Quality of work 2
3.33%
* Adjustment factor, see Appendix F, Table 3
** Defect rate: Observed defect rate (ODR) - Adjustment Factor (AF)
Note that in computing the defect rate, only those defects occurring in the
sample were counted. Defects outsidethe sample, such as validated customer
complaints, are not included when calculating the defect rate. It is
assumed that these defects are reflected in the results from the sample.
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