Problem 10-31 Large-scale integrated (LSI) circuit chips are made in one departm

Question

Problem 10-31

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 9% while the LTPD acceptable by the assembly department is 32%. 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 a, (Click to select)rejectaccept the lot if more than  defective.

Explanation / Answer

The parameters of the problem are:

AQL = 0.09

LPTD = 0.32

= 0.05

= 0.10

Find c and n

STEP 1: Determine acceptance number (c)

LTPD/AQL = 0.32/0.09 = 3.56

Find the ration in column 2 that is equal to or just greater than 3.56. The value from the column 2 is 4.057, which is associated with c = 4.

c = 4

STEP 2: Determine Sample Size

Find the value in column 3, that intersects with same row C = 4, which is 1.970.

Divide the column 3 value by AQL to obtain sample size as follows:

n = 1.970/0.09 = 22

Appropriate sample size = n = 22 units

Part 2:

22 chips will be inspected if more than 4 defective units are found, the lot will be rejected.

Randomly sample 22 chips and reject the lot if more than 4 defectives are identified.

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