Since we do not know the population standard deviation, we will use the t-distribution to construct the 90% confidence interval of the mean number of books people read. The value of 
with 1010 degrees of freedom and with alpha equals to 0.10 is 1.64
First, we need to solve for the margin of error, E.
The lower bound of the confidence interval is
The upper bound of the confidence interval is
Therefore, the 90% confidence interval is (13.94, 15.66).
We are 90% confident that the interval from 13.94 books to 15.66 books does contain the true value of the population mean number of books people read.
First, we need to solve for the margin of error, E.
The lower bound of the confidence interval is
The upper bound of the confidence interval is
Therefore, the 90% confidence interval is (13.94, 15.66).
We are 90% confident that the interval from 13.94 books to 15.66 books does contain the true value of the population mean number of books people read.