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9. A college financial advisor wants to estimate the mean cost of textbooks per quarter for students at the college. For the estimate to be useful, it should have a margin of error of 20 dollars or less. The standard deviation of prices is estimated to be around 100 dollars. How large of a sample size needs to be used to be 95% confident, with the given margin of error?

Respuesta :

JeanaShupp

Answer: 97

Step-by-step explanation:

Formula to compute the required sample size :

[tex]n= (\dfrac{\sigma\times z_{\alpha/2}}{E})^2[/tex]

, where [tex]\sigma[/tex] = standard deviation

E= Margin of error

[tex]z_{\alpha/2}[/tex] = Two tailed z-value.

Here, E= 20

[tex]\sigma[/tex] = 100

For 95% confidence level: [tex]z_{\alpha/2}[/tex] =1.96

Required sample size:

[tex]n=(\dfrac{100\times1.96}{20})^2\\\\=(5\times1.96)^2\\\\=96.04\approx97[/tex]

Hence, the required sample size : 97

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