Westonci.ca is the premier destination for reliable answers to your questions, provided by a community of experts. Connect with professionals ready to provide precise answers to your questions on our comprehensive Q&A platform. Connect with a community of professionals ready to help you find accurate solutions to your questions quickly and efficiently.

A simple random sample of electronic components wil be selected to test for the mean lifetime in hours. Assume that component lifetimes are normally distributed with population standard deviation of 16 hours. How many components must be sampled so that a 99% confidence interval will have margin of error of 3 hours

Sagot :

Answer:

189 components must be sampled.

Step-by-step explanation:

We have that to find our [tex]\alpha[/tex] level, that is the subtraction of 1 by the confidence interval divided by 2. So:

[tex]\alpha = \frac{1 - 0.99}{2} = 0.005[/tex]

Now, we have to find z in the Ztable as such z has a pvalue of [tex]1 - \alpha[/tex].

That is z with a pvalue of [tex]1 - 0.005 = 0.995[/tex], so Z = 2.575.

Now, find the margin of error M as such

[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]

Assume that component lifetimes are normally distributed with population standard deviation of 16 hours.

This means that [tex]\sigma = 16[/tex]

How many components must be sampled so that a 99% confidence interval will have margin of error of 3 hours?

n components must be sampled.

n is found when M = 3. So

[tex]M = z\frac{\sigma}{\sqrt{n}}[/tex]

[tex]3 = 2.575\frac{16}{\sqrt{n}}[/tex]

[tex]3\sqrt{n} = 2.575*16[/tex]

[tex]\sqrt{n} = \frac{2.575*16}{3}[/tex]

[tex](\sqrt{n})^2 = (\frac{2.575*16}{3})^2[/tex]

[tex]n = 188.6[/tex]

Rounding up:

189 components must be sampled.