Question

A researcher examines 4 sedimentary samples for mercury concentration. The mean mercury concentration for the sample data is 0.621 cc/cubic meter with a standard deviation of 0.0128. Construct the 80 % confidence interval for the population mean mercury concentration. Assume the population is approximately normal.

Lower endpoint:

Upper endpoint:

Answer 1

n = Sample Size = 4

= Sample Mean = 0.621

s = Sample SD = 0.0128

SE = s/

= 0.0128/ =0.0064

= 0.20

ndf = n - 1 = 4 - 1 = 3

From Table, critical values of t = 1.6377

Confidence Interval:

Lower endpoint = 0.621 - (1.6377 X 0.0064) = 0.621 - 0.0105 = 0.6105

Upper endpoint = 0.621 + (1.6377 X 0.0064) = 0.621 + 0.0105 = 0.6315

So,

Answers are:

Lower endpoint = 0.6105

Upper endpoint = 0.6315