3.... acceptance sampling

15,383 views

Published on

Published in: Technology, Business
1 Comment
16 Likes
Statistics
Notes
No Downloads
Views
Total views
15,383
On SlideShare
0
From Embeds
0
Number of Embeds
11
Actions
Shares
0
Downloads
1,460
Comments
1
Likes
16
Embeds 0
No embeds

No notes for slide

3.... acceptance sampling

  1. 1. ACCEPTANCE SAMPLING PRESENTED BY SREEDEVI K.N M.Sc INDUSTRIAL FISHERIES III SEMESTER
  2. 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. 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. 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.
  5. 5. SAMPLING PLANSATTRIBUTES SAMPLING VARIABLE SAMPLING1. SINGLE SAMPLING2. DOUBLE SAMPLING3. MULTIPLE SAMPLING4. SEQUENTIAL SAMPLING
  6. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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.

×