Respuesta :
Answer:
a) [tex]z = 1.645[/tex]
b) Lower endpoint: 0.422cc/m³
Upper endpoint: 0.452 cc/m³
Step-by-step explanation:
Population is approximately normal, so we can find the normal confidence interval.
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{1-0.9}{2} = 0.05[/tex]
Now, we have to find z in the Ztable as such z has a pvalue of [tex]1-\alpha[/tex].
So it is z with a pvalue of [tex]1-0.05 = 0.95[/tex], so [tex]z = 1.645[/tex]. This is the critical value, the answer for a).
Now, find M as such
[tex]M = z*\frac{\sigma}{\sqrt{n}}[/tex]
In which [tex]\sigma[/tex] is the standard deviation of the population and n is the size of the sample.
[tex]M = 1.645*\frac{0.0325}{\sqrt{12}} = 0.015[/tex]
The lower end of the interval is the sample mean subtracted by M. So it is 0.437 - 0.015 = 0.422cc/m³.
The upper end of the interval is the sample mean added to M. So it is 0.437 + 0.015 = 0.452 cc/m³.
b)
Lower endpoint: 0.422cc/m³
Upper endpoint: 0.452 cc/m³
