## Mean and standard deviation by stealth

This has been set to a group of students as homework (old fashioned term, but that is what it was) and I will evaluate the success of the mission in 10 days or so it being half term next week. The numerical answers are mean 101.9 and standard deviation 6.5.

I decided to turn the calculation into an exercise in following instructions as the particular student group was familiar with lab protocols. I then follow up with some explanation. There is a spreadsheet formula reference card in production, and I will be evangelising on the merits of symbolic notation soon enough. I do NOT teach the alternative algorithm as it is numerically unstable with data sets that have low variation.

OpenOffice note: The maths code used to produce the standard deviation formula was

SD = sqrt{{sum{(x-bar{x})^2}}over{N-1}}

I much prefer the OpenOffice formula editor to the more mouse directed one provided with a well known commercial package…