2.3) The value of repeat analyses

The precision of trace element single analyses on the laser ablation ICP-MS is on the order of 10% relative.
How much would the precision improve if the analysis is repeated 5 times to obtain a mean?

When conducting microprobe analysis you generally analyse the standard 5 times to improve the
accuracy of the calibration. For the following calibration results; calculate the count statistical error
for each analysis and the average relative precision from these 5 estimates of the count statistical 
error. What is the standard deviation on the full set? Why are they different?

Ti (cts)				
2601.4	
2598.7	
2610.3
2631.5
2606.8