1. Prepared by Anthony Lizza Penn State University
Acceptance Sampling
Prepared by
Anthony Lizza
Penn State University

2. What will be covered? What is acceptance sampling?
How/When would you use it in your organization?
Acceptance sampling explained.
How acceptance sampling works.
An exercise.
Summary
You will be informed with the general knowledge to better understand and implement acceptance sampling into your organization.

3. What is acceptance sampling?
Statistical quality control technique, where a random sample is taken from a lot, and upon the results of the sample taken the lot will either be rejected or accepted.
In general, acceptance sampling is an approach to test the conformance of the products you have produced. You can either test a few items or every item in the lot.
(LOT)-is the entire batch, group of items produced.

4. What is acceptance sampling?
Accept Lot
Ready for customers
Reject Lot
Not suitable for customers
Statistical Process Control(SPC)
Sample and determine if in acceptable limits
(LOT)-entire batch, group of items produced.

5. What is acceptance sampling?
Purposes
Determine the quality level of an incoming shipment or, at the end production
Ensure that the quality level is within the level that has been predetermined
Remember your main purpose is to sentence the lot basically to life or death. You will reject or accept it but not measure the quality of the product.

6. What is acceptance sampling?
Can be either 100% inspection, or a few items of a lot.
Complete inspection
Inspecting each item produced to see if each item meets the level desired
Used when defective items would be very detrimental in some way
Certain situations will tend to favor different sampling methods.

7. Acceptance Sampling method

8. What is acceptance sampling?
Problems with 100% inspection
Very expensive
When product must be destroyed to test
Inspection must be very tedious so defective items do not slip through inspection
Acceptance sampling is very favorable when weighing out the advantages and disadvantages associated with complete inspection. However, certain situations favor different approaches as stated earlier.

9. How/When would you use it?
Acceptance sampling advantages
Less handling damages
Fewer inspectors to put on payroll
100% inspection costs are to high
100% testing would take to long
The how and when slides will begin to show you and give you a respect towards the different approaches, not only to show you how and when to implement, but also why you should.

10. How/When would you use it?
Acceptance sampling disadvantages
Risk included in chance of bad lot “acceptance” and good lot “rejection”
Sample taken provides less information than 100% inspection
The disadvantages show shy acceptance sampling could be bad. You may be confused right now about what method to implement. You must choose which one would fit proportionately with your organizations procedures.

11. How/When would you use it?
Between your organization and outside world
Samples taken run through “filter,” either passing or rejecting it
Also filter from suppliers to you
Filter is a way of preventing defects from being issued to customers, and defects coming to you from suppliers.

12. How/When you would use it?
When products in use could be damaged easily
When using new suppliers
When new products produced
When current supplier in question
Testing whole lot could be harmful
These are a few situations in which your organization would find it worthy of using the acceptance sampling approach.

13. How/When you would use it?
Determine how many units, n, to sample from an lot
Determine maximum number of defective items, c, that can be found before the lot is rejected
Now you will begin to understand the variables and there meaning when doing the equating during the acceptance sampling process.

14. Acceptance sampling explained
Acceptable Quality levels(AQL)
Number of defect percentage allowed in a lot which can still be considered accepted(Type I error)
Lot Tolerance Percent Defective(LTPD)
Amount of defects that will come with a lot of goods(Type II error)
These are more terms you need to know when equating, Type I and II errors are explained in the next couple slides.

15. Acceptance sampling explained
Sampling Plan
Forms after n and c values have been found
Producers risk
Risk associated with a lot of acceptable quality rejected
More basically producers risk is the chance of the suppliers shipment being rejected by the organization when the shipment is good.
Consumers risk is the risk involved when sending products to consumers and assume the lot to be good, but it’s not.

16. Acceptance sampling explained
Consumers risk
Receive shipment, assume good quality, actually bad quality
Alpha
Type I error(producers risk)
Beta
Type II error(consumers risk)

17. Acceptance sampling explained
Sample size taken for your sampling plan C
Where rejections would occur when defects exceeded this percent
N is the number of products sampled.
C is where you would reject a lot if percentage of defects surpassed it.
OC is the graph showing the point where the lot would be accepted to.

18. Acceptance sampling explained
Operating characteristics curve(OC)
A graph, displaying standards at which shipments would be accepted
First
Determine AQL, a, LTPD, b,
Take LTPD/AQL, this gives you the n(AQL)

19. Acceptance sampling explained
Reference n(AQL) in the table
C will be given as well when referencing the table
Next
N(AQL/AQL)=n-sample size
C= reject if more percent defects more
The equations can be tricky but the exercise later will help
How to begin equating.

20. How acceptance sampling works
Two classifications of acceptance plans
Attributes(“go no-go”)
Variables
Acceptance Plans-
attributes
variables

21. How acceptance sampling works
Attributes(“go no-go”)
Defectives-product acceptability across range
Defects-number of defects per unit
Variable(continuous)
Usually measured by mean and standard deviation
Difference between defect and defectiveness in attributes.
Definitions of attributes and variables.

22. How acceptance sampling works
Remember
You are not measuring the quality of the lot, but, you are to sentence the lot to either reject or accept it
NOT MEASURING QUALITY, REJECTING OR ACCEPTING A LOT DEPENDING ON CERTAIN CIRCUMSTANCES.

23. An Exercise Determine the AQL, a, LTPD, B? Reference table provided- c
LTPD/ AQL
nAQL
44.890
.052 5
3.549
2.613 1
10.946
.0355 6
3.206
3.286 2
6.509
.0818 7
2.957
3.981 3
4.890
1.366 8
2.768
4.695 4
4.057
1.970 9
2.618
5.426
Remember the equations from earlier.
Answer and method:
LTPD/AQL=.03/.01=3 - these numbers were provided in the problem, the vendor has a 1% acceptable quality level and the manufacturer considers 3% defectives unacceptable.
N(AQL)=3.286 – you have to find the number closest rounded to three fro the previous equation.
C=6, from table
N(AQL)= 3.286/.01= 328.6, 329-round up
This means that you would take a random sample of 329 units for the specific lot and reject it if more than 6 units were defective.

24. An Exercise cont.
Assume a manufacturer purchases wire from an outside vendor. The wire vendor has an accepted quality level of 1% and accepts a 5% risk of rejecting lots below this level. The manufacturer considers lots with 3% defectives to be unacceptable and assumes a 10% risk of accepting a defective lot. Develop a sample plan for the manufacturer to be followed by the inspection personnel

25. Summary
Acceptance sampling is used by organizations to determine if there process’s are running within a controlled limit and to see if they should reject or accept lots

26. Summary
There are many basic terms you need to know to be able to understand acceptance sampling
SPC, Accepts Lot, Reject Lot, Complete Inspection, AQL, LTPD, Sampling Plans, Producers Risk, Consumers Risk, Alpha, Beta, Defect, Defectives, Attributes, Variables.

27. Summary Advantages/Disadvantages of acceptance sampling
Purpose of acceptance sampling
When to use acceptance sampling
Equations involved
Exercise
Notes pages have many beneficial hints and help better relate the material, the answer to the exercise is also located on a the notes page of the exercise.

28. Bibliography
(Foster, S.Thomas: “Managing Quality-An Integrative Approach:pgs :copyright 2001)
“Quality Control in Furniture Manufacturing”:Internet

29. Bibliography
“Process Analysis”:Internet
“Quality Control”: Internet