Question

Problem 10-31 (Algo) Large-scale integrated (LSI) circuit chips are made in one department of an electronics firm. These chips are incorporated into analog devices that are then encased in epoxy. The yield is not particularly good for LSI manufacture, so the AQL specified by that department is 20% while the LTPD acceptable by the assembly department is 52%. Assume the company is willing to accept a consumer's risk of 10 percent and a producer's risk of 5 percent. Use Exhibit 10.16 a. Find the sample size. (Round up your answer to the next whole number.) Sample size b. How would you tell someone to do the test? Randomly sample LSi using the sample size from part the lot if more than

Answer 1

Problem 10-31

AQL = 20%

LTPD = 52%

LTPD/AQL = 52%/20% = 2.6

Look for the value closest to 2.6 in the second column of the following table

Exhibit 10.16 Sampling Plan Table with Producers Risk = 0.05 and Consumers Risk = 0.10
C	LTPD/AQL	n(AQL)	n(LTPD)
0	44.89	0.052	2.334
1	10.946	0.355	3.886
2	6.509	0.818	5.324
3	4.89	1.366	6.68
4	4.057	1.97	7.992
5	3.549	2.613	9.274
6	3.206	3.286	10.535
7	2.957	3.981	11.772
8	2.768	4.695	12.996
9	2.618	5.426	14.205

The value closest to 2.6 is 2.618

and the corresponding value of c is 9 and value of n(AQL) is 5.426

where, c is the acceptance number

and n is the sample size. Therefore,

n = n(AQL)/AQL = 5.426/20% = 27

a)

Sample size =  27

b)

Randomly select LSI using the sample size from part a,   Reject   the lot if more than   9   defectives.