My first year classes have been learning about uncertainties and how to process data by doing the density of Plasticine lab. One thing I didn't anticipate was how long it would take the students to measure 5 Plasticine balls 5 times with a vernier calliper. After spending two 1 hour 20 minute lessons on the task most of them are now well into the processing part, which has been going fine for all the students with Excel installed on their computers. There have been the usual problems - using full stop when it should be comma or comma when it should be full stop and the annoying Excel date thing - but mostly it's gone well. At this rate I'll have done all my 4psow hours by the end of the month.