Trollet kommer från NORDTEST handbok om intern kvalitetskontroll TR569, den engelska finns här. Den svenska kan beställas från RISE, info@ri.se.
Once upon a time there were a lot of Trolls in the Nordic countries like the one you see on the title page. They were sometimes pestering us so we have a saying something like The Troll is up to mischief meaning there are some odd things going on which we do not understand like a control value in the red area in a QC chart.