One of the things that Matt Haigh looked at when considering the impact of item format (see previous post) was whether the presence of a picture made the question easier or harder. He started with a very simple multiple choice item:
Which of the following is a valid argument for using nuclear power stations?
- for maximum efficiency, they have to be sited on the coast
- they have high decommissioning costs
- they use a renewable energy source
- they do not produce gases that pollute the atmosphere
All the students received this question, but half had a version which showed a photograph of a nuclear power station. Not surprisingly, the students liked the presence of the photograph. The version with the photograph also had a slightly lower item difficulty (when calcualted by either Classical Test Theory and Item Response Theory paradigms), but not significantly so.
When compared with aspects of my work that I’ve already described briefly (it’s the dreaded sandstone question again – see Helpful and unhelpful feedback : a story of Sandstone) it is perhaps surprising that the presence of the photograph does not confuse people and so make the question more difficult. (more…)