There are two production lines in a factory. Each morning, 60 items from production line A and 80 items from production line B will be selected randomly for quality checking. The quality of each selected item will be classified as “good”, “average”, or “poor”. Today’s checking indicates that the percentage of items classified as “good”, “average”, and “poor” are 80%, 15%, and 5% for production line A and 60%, 25%, and 15% respectively for production line B.
(a)What percentage of items in the sample is classified as “good” and is from production line A?
(b)What percentage of items in the sample is classified as “average” or “poor”?
One item is randomly chosen from the sample for further inspection.
(c)What is the probability that this item is a “poor” item and from production line B?
(d)Suppose the one for further inspection is known as “good”. What is the probability that it is from production line A?
Maths
2010-11-03 9:58 am
回答 (1)
2010-11-04 2:54 am
✔ 最佳答案
Based on information provided, you can come up with the following table:Good Average Poor Total
Product A 48 9 3 60
Product B 48 20 12 80
Total 96 29 15 140
(a) % of 'good' and from A = 48/140 = 34.29%
(b)% of 'average' or ' poor' = (29 + 15)/140 = 31.43%
(c) P(Poor and from B) = 12/140 = 0.0857
(d) Sample known to be 'good' = 96, so P('Good' and from A) = 48/96 = 0.5
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