For each of the following sets of numbers, calculate a \(95 \%\) confidence interval for the mean ( \(\sigma\) not known); before going through the steps in calculating the confidence interval, the sample mean \(\left(\mathrm{X}^{-}\right)\)and standard deviation \((s)\) must first be calculated.

a. \(7,2,5,9,6,6\)

b. \(4,8,13,6,7,11,15,10\)

c. \(6,25,20,7,10,9,21,14,11,15\)

d. \(89,92,87,84,90,88,91,80,87,93,85\)