Answer: answer will be 72.50. To find the mean you just add up all the numbers and divide by how many numbers are there. 870.02/12=72.501666667.
Answer: The standard error of the mean = 0.5
Step-by-step explanation:
Given : Sample size : n = 144
Standard deviation : 
The formula to find the standard error of the mean is given by :-

i.e. 
Hence, the standard error of the mean =0.5
The numbers decrease by 6.
-1, -8, -14, -20, -26, -32, -38, -44, -50, -56, -62, -68, -74, -80, -86, -92, -98, -104, -110, -116, -122, -128, -134, -140, -146
D. is the answer :))))))))))))))))