Respuesta :
Answer:
The 85% confidence interval for the mean number of dresses purchased each year is (6.1, 6.3).
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 - 0.85}{2} = 0.075[/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 - 0.075 = 0.925[/tex], so Z = 1.44.
Now, find the margin of error 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 = 1.44\frac{1.1}{\sqrt{208}} = 0.1[/tex]
The lower end of the interval is the sample mean subtracted by M. So it is 6.2 - 0.1 = 6.1
The upper end of the interval is the sample mean added to M. So it is 6.2 + 0.1 = 6.3
The 85% confidence interval for the mean number of dresses purchased each year is (6.1, 6.3).
