A yield improvement study at a semiconductor manufacturing facility provided def
ID: 3441400 • Letter: A
Question
A yield improvement study at a semiconductor manufacturing facility provided defect data for a sample of 450 wafers. The following table presents a summary of the responses to two questions: "Was a particle found on the die that produced the wafer?" and "Is the wafer good or bad?"
Quality of Wafer
Condition of Die
No Particles
Particles
Totals
Good
320
14
334
Bad
80
36
116
Totals
400
50
450
Referring to the above table, if a wafer is selected at random, what is the probability that :
a. it was produced from a die with no particles?
b. it is a bad wafer and was produced from a die with no particles?
c. it is a bad wafer or was produced from a die with particles?
d. Explain the difference in the results in (b) and (c).
Quality of Wafer
Condition of Die
No Particles
Particles
Totals
Good
320
14
334
Bad
80
36
116
Totals
400
50
450
Explanation / Answer
a)
P(no particles) = 400/450 = 0.8888888889
b)
P(bad and no particles) = 80/450 = 0.177777778
c)
P(bad OR with particles) = (80 + 36 + 15)/450 = 0.291111111
d)
B used AND, that means, simultaneously, it has to be a bad wafer and no particles.
C used OR, that means, it suffices that EITHER it is a bad wafer OR with particles.
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