Question 1120011
The half interval is z*sigma/sqrt (n)
This is 1.96*110/sqrt(70) for a 95% CI
=$25.77
interval is $420+/- $25.77
($394.23, $445.77)
This means while we don't know the exact mean, short of surveying every lawyer, we can be very confident that the true value lies in this interval.  We are using confidence, because the true value either DOES or DOES NOT lie in the interval, and that is not a useful probability statement.