How the sciences work
At the start of marking a Senior marker checks the guidelines against a group of sample papers and makes recommendations for changes
2 or 3 pilot markers come in and check the guidelines against more papers and recommend any changes and identify common types of response or errors in responses.
Markers come in and are taught the scheme and for the first few days all papers are double marked, either by the marker and senior marker or check markers.
The first thing markers do is check that all papers are present and in correct order.
Random papers are sent round between markers to check to see if they are consistent.
After first couple of days the papers are check marked. That is at least one paper from a group is checked. The longer the question, the more papers that are checked.
During all marking, any contentious or border line answers are discussed with at least one other marker. That also goes for answers that can't be read easily.
If a group is more than about 25, then it is split into two or more groups, to ensure different markers do part of it, to enable statistical checking.
All marking is scanned and senior marker is provided with statistics that show if a markers average is different to the group, if sd is different or if they are awarding a certain mark more than others. If that is the case, then the senior markers discusses it with the marker and checks more papers.
If at the end of marking a persons paper is statistically different to where expected for their group or for a specific question, then they are check marked again by the senior marker.