A process yields 10% defective items. For testing purposes, 100 items

Jason Watson

Jason Watson

Answered question

2021-11-17

A process yields 10% defective items. For testing purposes, 100 items are randomly selected from the process. A normal distribution may be approximated in order to get the probability of any event.
- What is the probability that the number of defectives exceeds 13?
- What is the probability that the number of defectives is less than 8?

Answer & Explanation

Mary Moen

Mary Moen

Beginner2021-11-18Added 14 answers

Step 1
Let, n be the number of trials(n) =100
Success Probability(p) =10%
=10100
=0.1
Failure probability(q) =1p
=10.1
=0.9
Mean of binomial distribution,
μ=np
=100×0.1
=10
Standard deviation of binomial distribution is,
σ=npq
=100×0.1×0.9
=3
Step 2
a) Probability that the number of defectives exceeds 13:
We have to find the area to the right of x=13.5.
z=xμσ
=13.5103
=1.1666
1.17
Therefore, P(X>13)=P(Z>1.17)
=1P(Z<1.17)
=10.879
=0.1210
The probability that the number of defectives exceeds 13 is 0.1210.
Step 3
b) Probability that the number of defectives is less than 8:
We have to find the area to the left of x=7.5.
z=xμσ
=7.5103
=0.83
Therefore, P(X<8)=P(Z<0.83)
=0.2033
The probability that the number of defectives is less than 8 is 0.2033.

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