The data cited is in the attachment.
Answer: 308.2±106.4
Step-by-step explanation: To construct a confidence interval, first calculate mean (μ) and standard deviation (s) for the sample:
μ = Σvalue/n
μ = 308.2
s = √∑(x - μ)²/n-1
s = 147.9
Calculate standard error of the mean:
[tex]s_{x} = \frac{s}{\sqrt{n} }[/tex]
[tex]s_{x}[/tex] = [tex]\frac{147.9}{\sqrt{12} }[/tex]
[tex]s_{x}[/tex] = 42.72
Find the degrees of freedom:
d.f. = n - 1
d.f. = 12 - 1
d.f. = 11
Find the significance level:
[tex]\frac{1-0.97}{2}[/tex] = 0.015
Since sample is smaller than 30, use t-test table and find t-score:
[tex]t_{11,0.015}[/tex] = 2.4907
E = t-score.[tex]s_{x}[/tex]
E = 2.4907.42.72
E = 106.4
The interval of confidence is: 308.2±106.4, which means that dental insurance plan varies from $201.8 to $414.6.
