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Binomial & Poisson Distributions · Question 50 of 68

What is the mean number of defective bulbs in a box?

Question 50

EasyOriginal question

A factory finds that 5% of its LED bulbs are defective. They are packed in boxes of 10, and the number of defective bulbs in a box is taken to follow a Poisson distribution. (Take e−0.5=0.6065e^{-0.5} = 0.6065.)

What is the mean number of defective bulbs in a box?

Options for question 50

Show the answer and explanation
CorrectNot quiteAnswer B

Correct answer: B

Explanation

  1. λ=np=10×0.05\lambda = np = 10 \times 0.05.

  2. λ=0.5\lambda = 0.5.

Worth noting

0.05 is the chance for one bulb; a box holds 10.

Concept
The Poisson mean \(\lambda = np\)
Typical time
90 s
Your time
—
The rule this testsThe Poisson distribution
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