Download a set of instructions written in English about how to calculate the mean and standard deviation of a data set.

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…

Download a PDF file with 10 data sets that can be used to illustrate a variety of statistical techniques

Useful pages:

• Selected Data-sets from Publications by Martin Bland
• A stroop effect lap report with actual data
• One for the tree huggers – I always loved that picture of a road tunnel in the trunk of a Giant Redwood as a child
• Favourite Data sets from drugs research (Bradstreet)

A spreadsheet with all the data sets is on its way so I can demonstrate how to analyse the data once we have decided what methods are appropriate. I like having a dialogue and a spreadsheet instead of Yet Another PowerPoint!

Download a two sided handout on finding the five number summary for a set of data

The five numbers are the maximum, the minimum, the median and the upper and lower quartiles. This set of numbers can tell you about the central tendency of your data, the spread, the extreme values, and provide low order information about the shape of the distribution. The blood pressure data sets came from Dr Bradstreet’s Favorite Datasets in Early and Late phases in Drug Research.

Box and whisker plot next, so I can explain how to interpret the five number summary. This series is part of a few sessions I’m planning for some degree students. The box and whisker illustration here was produced using the Gnumeric spreadsheet – it has a useful selection of statistical graphs and can export graphs as SVG or in a variety of bitmaps. Version 1.9.9 is in the Ubuntu 9.10 repositories.