Answer
margin of error = 4.27 and sample mean = 25.88
Work Step by Step
1) Find the width of the interval
30.15 - 21.61 = 8.54
2) Find the margin of error by dividing the width by two:
$\frac{8.54}{2}$ = 4.27
3) Subtract the margin of error from upper bound to find mean
30.15 - 4.27 = 25.88
Therefore, margin of error = 4.27 and sample mean = 25.88
