An electrical firm manufactures light bulbs that have a length of life that is approximately normally...

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An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a stan

math Statistics-And-Probability

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Answer 1

Answer #1

z value for 99% CI is 2.576 as P(-2.576<z<2.576)=0.99

Margin of Error is E=4

Standard deviation is $\sigma=25$

Hence we will find n using formula of E

$E=z*\frac{\sigma }{\sqrt{n}}$

So $n=(\frac{z*\sigma}{E})^2=(\frac{2.576*25}{4})^2=259.21=260$

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Answer 2

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