my first post so hi all.
I have been tasked with finding the standard deviation of a set of data. I am no mathematician and could use some help.
We are changing the way the business charges for delivery.
I have created a report of the year-to-date orders (140k lines in excel).
I have applied the old charging and new charging to each line and then calculated the difference.
I have the average difference (-1.03) and the standard deviation (40.25).
I want to show (I think) how many orders (as a percentage??) fall within 1 stdDev of the mean, how many fall with in 2 stdDevs and so on.
Can anyone please point me in the right direction.