The following data represent the concentration of dissolved organic carbon(mg/L) collected from 20 samples of organic soil. Assume that the population is normally distributed. Complete parts(a) through(c) on the right.

11.90

29.80

27.10

16.51

11.40

8.81

11.90

20.46

14.90

33.67

30.91

14.86

16.87

15.35

9.72

19.80

14.86

8.09

16.87

18.30

(a) Find the sample mean.

The sample mean is

17.60

17.60.

(Round to two decimal places asneeded.)

(b) Find the sample standard deviation.

The sample standard deviation is

7.44

7.44.

(Round to two decimal places asneeded.)

(c) Construct a 99% confidence interval for the population mean .

The 99% confidence interval for the population mean is ...( , )

(Round to two decimal places asneeded.)