
Answer & Step-by-step explanation:
The confidence interval formula is: Â
I (1-alpha) (μ)= mean+- [(t(n-1))* S/sqrt(n)] Â
alpha= is the proportion of the distribution tails that are outside the confidence interval. In this case, 5%. Â
t(n-1)= t(34)= is the critical value of the t distribution with n-1 degrees of freedom for an area of alpha/2 (2.5%). In this case is 2.032 Â
S= sample standard deviation because the problem does not specify that the standard deviation is from the population. In this case $17.32
mean= $63.57
n= number of observations =35
Then, the confidence interval (90%): Â
I 95%(μ)= 63.57+- [2.032*(17.32/sqrt(35)) Â
I 95%(μ)= 63.57+- [5.95) Â
I 95%(μ)= [63.57-5.95; 63.57+5.95] Â
I 95%(μ)= [57.62; 69.52] Â