Scaling API-first – The story of a global engineering organization
3.... acceptance sampling
1. ACCEPTANCE
SAMPLING
PRESENTED BY
SREEDEVI K.N
M.Sc INDUSTRIAL FISHERIES
III SEMESTER
2. INTRODUCTION
Quality control is an activity in which measures are
taken to control quality of future output.
Sampling refers to observation of a population or
lot for the purpose of obtaining some information
about it.
Acceptance sampling is a quality control technique.
3. DEFINITION
Acceptance sampling is defined as sampling
inspection in which decisions are made to accept
or reject products or services.
It is a decision making tool by which a
conclusion is reached regarding the acceptability
of lot.
4. ADVANTAGES
Acceptance sampling eliminates or rectifies poor lots &
improve overall quality of product.
Reduces inspection costs & risk.
In inspection of sample greater care will be taken so
that results may be more accurate.
A rejected lot is frequently a signal to the manufacturer
that the process should be improved.
It provides a no of alternative plans in which a single
sample is taken, two or indefinite no of samples may be
taken from a single lot.
6. ATTRIBUTES SAMPLING PLAN
Attributes sampling is most commonly used,
more than 1 type of quality characteristics can be
considered for each sample.
Measurements are simpler to make.
It requires a larger sample size than variables
sampling plan.
7. SINGLE SAMPLING
A plan in which inspector is forced to make a
decision concerning acceptability of a lot or batch
on the basis of inspection of units in one sample
taken from that lot.
It can be described in terms of 3 constants.
N,the lot size
n,the sample size
c,the acceptance number
c is the maximum allowable defects in sample
If sample contains c or fewer defectives, lot will be
accepted & if it contains more than c lot will be
rejected.
8. DOUBLE SAMPLING
These are characterized by two sample size along with
two sets of acceptance rejection numbers.
The two sample sizes may or may not be equal.
It can be described in terms of c1,c2,n1,n2
MULTIPLE SAMPLING
• In this 3 or more samples might be taken
before a decision is reached regarding the
acceptability of a lot.
• It results in smaller average sample size.
9. SEQUENTIAL SAMPLING
An extreme case of multiple sampling in which
sampling might continues until the lot is exhausted.
It calls for inspection on an item by item basis.
Decision is made after each item is inspected
concerning whether lot should be accepted or rejected
or sampling continued.
Sampling & decision making continues until a clear cut
decision is obtained either to accept or reject.
10. VARIABLE SAMPLING
Variables plan need measurement type data &
decision must be based only on one such
measurement characteristics.
It is efficient because variables carry more
information than attributes.
Based on mean & standard deviation
characteristics.
They are difficult to use.
11. OPERATING CHARACTERISTIC
CURVE (oc)
A curve which serves to describe an acceptance
plan in terms of probability of accepting lots of
various quality levels with the plan.
Pa =probability of accepting a lot
P` =actual proportion of defectives
pa
p`
12. SAMPLING RISKS
Both producer & consumer will agree on two
proportions to represent the acceptable
proportion of defectives in the lot.
AQL(accaptable quality level) : it represents the maxi
proportion of defectives acceptable by consumer.
LTPD(lot tolerance percent defective): it represents
the mini proportion of defectives which consumer
finds unacceptable.
13. AVERAGE OUTGOING QUALITY
AOQ is the average quality in terms of fraction or %
defectives for inspection operations.
These are done under 2 conditions such as rejected lots
be screened &all defectives that contain be replaced by
good articles, lot sizes of product be constant.
The maxi value of AOQ is average outgoing quality
limit(AOQL).
Each acceptance sampling plan can be described in
terms of AOQL it will generate.
14. ACCEPTANCE SAMPLING SYSTEMS
American national standard, sampling procedures and
tables for inspection by attributes is a sampling system
indexed by lot size ranges, inspection levels AQLs.
The use of sampling schemes defined in this system will
constrain the producer to provide product of quality at
or better than selected AQL.
Dodge Romig system, Dodge Romig sampling
inspection tables are designed to minimize average total
inspection for a given AOQL.
15. CONCLUSION
Acceptance sampling is a statistical procedure used to
determine whether to accept or reject a production lot of
material.
A wide variety of sampling plans are available.plans have
an accepted AQL & a rejected LTPD & an AOQL.
Acceptance sampling tables are there to supply a set of
accepted procedures with known properties &verified
results.
Sampling provides rational means of verification that a
production lot confirms with requirements of technical
specifications.