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Gears produced by a grinding process are categorized
Chapter 4, Problem 14E(choose chapter or problem)
Gears produced by a grinding process are categorized either as conforming (suitable for their intended purpose), downgraded (unsuitable for the intended purpose but usable for another purpose), or scrap (not usable). Suppose that 80% of the gears produced are conforming, 15% are downgraded, and 5% are scrap. Ten gears are selected at random.
a. What is the probability that one or more is scrap?
b. What is the probability that eight or more are not scrap?
c. What is the probability that more than two are either downgraded or scrap?
d. What is the probability that exactly nine are either conforming or downgraded?
Questions & Answers
QUESTION:
Gears produced by a grinding process are categorized either as conforming (suitable for their intended purpose), downgraded (unsuitable for the intended purpose but usable for another purpose), or scrap (not usable). Suppose that 80% of the gears produced are conforming, 15% are downgraded, and 5% are scrap. Ten gears are selected at random.
a. What is the probability that one or more is scrap?
b. What is the probability that eight or more are not scrap?
c. What is the probability that more than two are either downgraded or scrap?
d. What is the probability that exactly nine are either conforming or downgraded?
ANSWER:Solution 14E
Step1 of 5:
We have random variable X which presents the number of gears that are scrap among the ten selected. Here X follows binomial distribution with parameters “n and p” that is X B(n, p),
The probability mass function of binomial distribution is given by
, x = 0,1,2,...,n.
Where,
n = sample size
= 10
x = random variable
p = probability of success
= 5%
= 0.05.
q = 1 - p (probability of failure)
= 1 - 0.05
= 0.95
Here our goal is:
a).We need to find the probability that one or more is scrap.
b).We need to find the probability that eight or more are not scrap.
c).We need to find the probability that more than two are either degraded or scrap.
d).We need to find the probability that exactly nine are either conforming or degraded.
Step2 of 5:
a).
P(One or more is scrap) = P(X1)
= 1 - P(X < 1)
= 1 - P(X = 0)
Consider,
P(X) =
P(X = 0) =
= (1)(1)(0.5987)
= 0.5987
Now,
P(one or more is scrap) = 1 - P(X = 0)
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