Page 166 - DMGT501_OPERATIONS_MANAGEMENT

Operations Management

Notes 3. Final Inspection: Final inspection of finished goods before these are despatched to next
stage of production or customer helps in locating various assignable causes and taking
suitable remedial actions.
(a) Errors associated with inspection
The errors erupt in due to the followings:
(i) Lack of understanding among standards of inspection.
(ii) Lack of consistency among various inspectors.
(iii) Improper sampling from the source population.
The errors at (i) & (ii) can be minimised but not eliminated altogether whereas the
error at (iii) can be eliminated through the choice of a correct sampling plan.
(b) Differences between 100% inspection and Sampling inspection

Table 6.3: Differences between 100% Inspection and Sampling Inspection

Hundred per cent Inspection Sampling Inspection
1. Total cost of inspection is very 1. As volume of inspection is very low and
high and at times it is hence total cost of inspection involved is
prohibitive. low.
2. This inspection is subject to 2. The sampling inspection is based on
errors due to operator’s scientific sampling plan system and hence
fatigue, negligence and due to is free from such errors and results can be
poor supervision by inspectors produced accurately.
and results cannot be
predicted with accuracy.
3. No Sampling error. 3. As the method is based on sample drawn
from the population, hence it is to
sampling error. However, subjected the
magnitude of sampling error can be
estimated.
4. This method of inspection is 4. Sampling inspection is the only way of
not at all suitable for inspecting for a destructive test.
destructive testing.

Thus, we may infer that sampling inspection is generally superior to hundred per cent inspection.

Task What is your perception of quality? How do you measure quality of your work?

6.5 Process Capability Defined

The Process Capability may be defined as the capability of a process. This can be evaluated from
the data which is free from assignable causes and hence the extent of variation exhibited by it is
only under the influence of the chance causes alone. In case it is not possible to remove the
assignable causes of, at least, we should get these (assignable) causes segregated through ‘Tests
of Significance’ the difference between the reference value and the measured value of samples.
The number of units in each sample is called ‘Sample Size’.

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