1. Industrial Quality Management
Acceptance Testing

2. Next Week
Important Review for Final Exam
Please remember to attend

3. Acceptance Testing Receive Material Inspect it
Accept / Reject based on inspection
Not the best way
Government & Military may require it
It may be a temporary step to solve a problem
Tends to Accept very good material & reject very bad material
Does not work so well with medium quality material

4. Example 1 Given: defect rate for acceptance is not to exceed 5%
A box has 95 good switches and 5 bad switches (should be accepted)
What is the probability of inspecting 20 of the switches & accepting the group?
2 cases & they are:____
P(no defects) = (0.95)20
(0.3585)
P(1 defect) = (0.05)(0.95)19 =
There are 20 ways to do this
20( ) =
P(accept) = =
26.41% probability of rejecting good material

5. OR Rule vs. AND rule
If we can use the word “AND” to describe our case:
Multiply probabilities
If we can use the word “OR” to describe our case:
Add probabilities
Go back to the last slide to see this

6. Example 2 Given: defect rate for acceptance is not to exceed 5%
A box has 97 good switches and 3 bad switches (should be accepted)
What is the probability of inspecting 20 of the switches & rejecting the group?
2 cases & they are:____
Please work your solution:

7. Example 3 Given: defect rate for acceptance is not to exceed 5%
A box has 90 good switches and 10 bad switches (should be rejected)
What is the probability of inspecting 20 of the switches & rejecting the group?
2 cases & they are:____
Please work your solution:

8. Example 4 Given: defect rate for acceptance is not to exceed 5%
A box has 190 good switches and 10 bad switches (should be accepted)
What is the probability of inspecting 40 of the switches & rejecting the group?
3 cases & they are:____
How many ways are there to get 2 defects?
C40,2 = 40!/(2! x 38!)
Please work your solution:

9. Poisson Probability Curve
n is number of samples inspected
c is the maximum number of defective allowed
p is the proportion of defective items in the group
Pa is the probability of accepting the group
Example:
From a group of 200 items with p = 0.05, c=7
What is the probability of accepting this group?

10. MIL STD 105D

11. MIL STD 105D Example Levels of Inspection Find your group size
I Relaxed
II Normal
III Tightened
Find your group size
How many must you inspect?
What is your level of quality?
Get the acceptance / rejection criteria
Given:
Batch of 500 resistors
Bad resistors are not to exceed 4%
Normal Inspection
How many resistors will you inspect?
How many defective resistors are allowed before you must reject?

12. MIL STD 105D Example What happens if you tighten the inspection?
What happens if you loosen the inspection?
What happens if you can accept a defect rate of 6.5% with normal inspection?
What happens if you can only accept a defect rate of 2.5% with normal inspection?