"A teller at a drive-up window at a bank had the following service time (in minutes) for 20 randomly selected customers:
SAMPLE
1 2 3 4
4.5 4.6 4.5 4.7
4.2 4.5 4.6 4.6
4.2 4.4 4.4 4.8
4.3 4.7 4.4 4.5
4.3 4.3 4.6 4.9
If the process parameters are unknown, estimate its mean and standard deviation.