3.... acceptance sampling

1. ACCEPTANCE ACCEPTANCE
SAMPLINGSAMPLING
PRESENTED BYPRESENTED BY
SREEDEVI K.NSREEDEVI K.N
M.Sc INDUSTRIAL FISHERIESM.Sc INDUSTRIAL FISHERIES
III SEMESTERIII SEMESTER

2. INTRODUCTIONINTRODUCTION
Quality control is an activity in which measures are Quality control is an activity in which measures are
taken to control quality of future output.taken to control quality of future output.
Sampling refers to observation of a population or Sampling refers to observation of a population or
lot for the purpose of obtaining some information lot for the purpose of obtaining some information
about it.about it.
Acceptance sampling is a quality control technique.Acceptance sampling is a quality control technique.

3. DEFINITIONDEFINITION
Acceptance sampling is defined as sampling Acceptance sampling is defined as sampling
inspection in which decisions are made to accept inspection in which decisions are made to accept
or reject products or services.or reject products or services.
It is a decision making tool by which a It is a decision making tool by which a
conclusion is reached regarding the acceptability conclusion is reached regarding the acceptability
of lot.of lot.

4. ADVANTAGESADVANTAGES
Acceptance sampling eliminates or rectifies poor lots & Acceptance sampling eliminates or rectifies poor lots &
improve overall quality of product.improve overall quality of product.
Reduces inspection costs & risk.Reduces inspection costs & risk.
In inspection of sample greater care will be taken so In inspection of sample greater care will be taken so
that results may be more accurate.that results may be more accurate.
A rejected lot is frequently a signal to the manufacturer A rejected lot is frequently a signal to the manufacturer
that the process should be improved.that the process should be improved.
It provides a no of alternative plans in which a single It provides a no of alternative plans in which a single
sample is taken, two or indefinite no of samples may be sample is taken, two or indefinite no of samples may be
taken from a single lot.taken from a single lot.

5. SAMPLING PLANS
ATTRIBUTES SAMPLING VARIABLE SAMPLING
1.SINGLE SAMPLING
2.DOUBLE SAMPLING
3.MULTIPLE SAMPLING
4.SEQUENTIAL
SAMPLING

6. ATTRIBUTES SAMPLING PLANATTRIBUTES SAMPLING PLAN
Attributes sampling is most commonly used, Attributes sampling is most commonly used,
more than 1 type of quality characteristics can be more than 1 type of quality characteristics can be
considered for each sample.considered for each sample.
Measurements are simpler to make.Measurements are simpler to make.
It requires a larger sample size than variables It requires a larger sample size than variables
sampling plan.sampling plan.

7. SINGLE SAMPLINGSINGLE SAMPLING
A plan in which inspector is forced to make a A plan in which inspector is forced to make a
decision concerning acceptability of a lot or batch decision concerning acceptability of a lot or batch
on the basis of inspection of units in one sample on the basis of inspection of units in one sample
taken from that lot.taken from that lot.
It can be described in terms of 3 constants.It can be described in terms of 3 constants.
 N,the lot sizeN,the lot size
n,the sample sizen,the sample size
c,the acceptance number c,the acceptance number
c is the maximum allowable defects in samplec is the maximum allowable defects in sample
If sample contains c or fewer defectives, lot will be If sample contains c or fewer defectives, lot will be
accepted & if it contains more than c lot will be accepted & if it contains more than c lot will be
rejected. rejected.

8. DOUBLE SAMPLINGDOUBLE SAMPLING
These are characterized by two sample size along with These are characterized by two sample size along with
two sets of acceptance rejection numbers.two sets of acceptance rejection numbers.
The two sample sizes may or may not be equal.The two sample sizes may or may not be equal.
It can be described in terms of c1,c2,n1,n2It 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 SAMPLINGSEQUENTIAL SAMPLING
An extreme case of multiple sampling in which An extreme case of multiple sampling in which
sampling might continues until the lot is exhausted.sampling might continues until the lot is exhausted.
It calls for inspection on an item by item basis.It calls for inspection on an item by item basis.
Decision is made after each item is inspected Decision is made after each item is inspected
concerning whether lot should be accepted or rejected concerning whether lot should be accepted or rejected
or sampling continued.or sampling continued.
Sampling & decision making continues until a clear cut Sampling & decision making continues until a clear cut
decision is obtained either to accept or reject.decision is obtained either to accept or reject.

10. VARIABLE SAMPLINGVARIABLE SAMPLING
Variables plan need measurement type data & Variables plan need measurement type data &
decision must be based only on one such decision must be based only on one such
measurement characteristics.measurement characteristics.
It is efficient because variables carry more It is efficient because variables carry more
information than attributes.information than attributes.
Based on mean & standard deviation Based on mean & standard deviation
characteristics.characteristics.
They are difficult to use.They are difficult to use.

11. OPERATING CHARACTERISTIC OPERATING CHARACTERISTIC
CURVE (oc)CURVE (oc)
A curve which serves to describe an acceptance A curve which serves to describe an acceptance
plan in terms of probability of accepting lots of plan in terms of probability of accepting lots of
various quality levels with the plan.various quality levels with the plan.
p`
pa
Pa =probability of accepting a lot
P` =actual proportion of defectives

12. SAMPLING RISKSSAMPLING RISKS
Both producer & consumer will agree on two Both producer & consumer will agree on two
proportions to represent the acceptable proportions to represent the acceptable
proportion of defectives in the lot.proportion of defectives in the lot.
AQL(accaptable quality level) : it represents the maxi AQL(accaptable quality level) : it represents the maxi
proportion of defectives acceptable by consumer.proportion of defectives acceptable by consumer.
LTPD(lot tolerance percent defective): it represents LTPD(lot tolerance percent defective): it represents
the mini proportion of defectives which consumer the mini proportion of defectives which consumer
finds unacceptable.finds unacceptable.

13. AVERAGE OUTGOING QUALITYAVERAGE OUTGOING QUALITY
AOQ is the average quality in terms of fraction or % AOQ is the average quality in terms of fraction or %
defectives for inspection operations.defectives for inspection operations.
These are done under 2 conditions such as rejected lots These are done under 2 conditions such as rejected lots
be screened &all defectives that contain be replaced by be screened &all defectives that contain be replaced by
good articles, lot sizes of product be constant.good articles, lot sizes of product be constant.
The maxi value of AOQ is average outgoing quality The maxi value of AOQ is average outgoing quality
limit(AOQL).limit(AOQL).
Each acceptance sampling plan can be described in Each acceptance sampling plan can be described in
terms of AOQL it will generate.terms of AOQL it will generate.

14. ACCEPTANCE SAMPLING SYSTEMSACCEPTANCE SAMPLING SYSTEMS
American national standardAmerican national standard, sampling procedures and , sampling procedures and
tables for inspection by attributes is a sampling system tables for inspection by attributes is a sampling system
indexed by lot size ranges, inspection levels AQLs.indexed by lot size ranges, inspection levels AQLs.
The use of sampling schemes defined in this system will The use of sampling schemes defined in this system will
constrain the producer to provide product of quality at constrain the producer to provide product of quality at
or better than selected AQL.or better than selected AQL.
Dodge Romig systemDodge Romig system, Dodge Romig sampling , Dodge Romig sampling
inspection tables are designed to minimize average total inspection tables are designed to minimize average total
inspection for a given AOQL.inspection for a given AOQL.

15. CONCLUSIONCONCLUSION
Acceptance sampling is a statistical procedure used to Acceptance sampling is a statistical procedure used to
determine whether to accept or reject a production lot of determine whether to accept or reject a production lot of
material.material.
A wide variety of sampling plans are available.plans have A wide variety of sampling plans are available.plans have
an accepted AQL & a rejected LTPD & an AOQL.an accepted AQL & a rejected LTPD & an AOQL.
Acceptance sampling tables are there to supply a set of Acceptance sampling tables are there to supply a set of
accepted procedures with known properties &verified accepted procedures with known properties &verified
results.results.
Sampling provides rational means of verification that a Sampling provides rational means of verification that a
production lot confirms with requirements of technical production lot confirms with requirements of technical
specifications.specifications.