Question:
It is known that 20% of products on a production line are defective. Products are inspected until first defective is encountered. a) What is the probability that the experimenter must inspect six products to find a defective product?
Answer:
P(x = 6) = 0.0655
P(x = 6) = 6.55%
Explanation:
It is given that 20% of products on a production line are defective.
p = 0.20
Then
q = 1 - p = 1 - 0.20 = 0.80
Which means that 80% of products on the production line are not defective.
We want to find out the probability that the experimenter must inspect six products to find a defective product.
Let x is the number of inspections to get a defective product.
P(x = 6) = ?
If out of 6 inspections 1 is defective then it means 5 are not defective
so the probability is
P(x = 6) = p¹ × q⁵
P(x = 6) = 0.20¹ × 0.80⁵
P(x = 6) = 0.20 × 0.32768
P(x = 6) = 0.0655
P(x = 6) = 6.55%
Therefore, there is 6.55% chance that the experimenter finds a defetive product in 6 inspections.