A group of concerned citizens are collecting water samples from a local river to detect the level of nitrogen in the water. They plan to take samples every day for a month and then will divide the sum by the number of days they sampled. What is the group trying to do?
a) determine the mean level of nitrogen in the water (X)
b) determine the average level of nitrogen in the water (X)
c) determine the confidence level of the sample
d) both determine the mean level of nitrogen in the water and determine the average level of nitrogen in the water
e) both determine the average level of nitrogen in the water and determine the confidence level of the sample