Gas chromatography is a sensitive technique used by chemists to measure small amounts of compounds. The response of a gas chromatograph is calibrated by repeatedly testing specimens containing a known amount of the compound to be measured. A calibration study for a specimen containing 1 nanogram (ng) (that's 10-9 gram) of a compound gave the following response readings:

21.6 20.0 25.0 21.9

Question

Gas chromatography is a sensitive technique used by chemists to measure small amounts of compounds. The response of a gas chromatograph is calibrated by repeatedly testing specimens containing a known amount of the compound to be measured. A calibration study for a specimen containing 1 nanogram (ng) (that's 10-9 gram) of a compound gave the following response readings:

21.6	20.0	25.0	21.9

anonymous · Answer

The response is known from experience to vary according to a normal distribution unless an outlier indicates an error in the analysis. Estimate the mean response to 1 ng of this substance, and give the margin of error for your choice of confidence level. Then explain to a chemist who knows no statistics what your margin of error means.

jordan123321 · Answer

what do you think

anonymous · Answer

Please help would appreciate it :)

anonymous · Answer

@jordan123321 I know I need to find the mean and standard deviation of the data but I'm not sure what I have to do from there. 
Mean: 21.6+20.0+25.0+21.9/4=22.125
SD:1.81