Answer:
[tex]E = 3.46\ movies[/tex]
Step-by-step explanation:
The formula to find the error is:
[tex]E = z_{\frac{\alpha}{2}}\frac{\sigma}{\sqrt{n}}[/tex]
Where:
[tex]\sigma[/tex] is the standard deviation
n is the sample size
So
n = 80 people
[tex]\sigma[/tex] = 12 movies
Then
[tex]1- \alpha[/tex] = confidence level = 0.99
[tex]\alpha= 1-0.99[/tex]
[tex]\alpha = 0.01\\\\\frac{\alpha}{2} = 0.005[/tex]
We look for the Z value: [tex]Z_{0.005}[/tex]
[tex]Z_{0.005}=2.58[/tex] Looking in the normal standard tables
Therefore:
[tex]E =2.58*\frac{12}{\sqrt{80}}\\\\E = 3.46\ movies[/tex]
