For a group experiment, your science class measured the fine-particulate concentrations in the air at random places around campus, and estimated a sample average of 12 μg/m3 (micrograms per cubic meter). If 196 readings were taken, and the standard deviation of the sample measurements was 3.5 μg/m3, you are 99.7% confident that actual concentration of fine particulates at the school is __________ .

A. 11.25 μg/m3 – 12.75 μg/m3
B. 5 μg/m3 – 19 μg/m3
C. 1.5 μg/m3 – 22.5 μg/m3
D. 11.5 μg/m3 – 12.5 μg/m3

Question

For a group experiment, your science class measured the fine-particulate concentrations in the air at random places around campus, and estimated a sample average of 12 μg/m3 (micrograms per cubic meter). If 196 readings were taken, and the standard deviation of the sample measurements was 3.5 μg/m3, you are 99.7% confident that actual concentration of fine particulates at the school is __________ .

 		A.	11.25 μg/m3 – 12.75 μg/m3
 		B.	5 μg/m3 – 19 μg/m3
 		C.	1.5 μg/m3 – 22.5 μg/m3
 		D.	11.5 μg/m3 – 12.5 μg/m3