Crossing the liminal space: students’ understanding of confidence intervals

This paper describes responses first-year university students gave to a survey asking them about their understanding of Confidence Intervals, after their first introduction to the topic in a statistics course at two tertiary institutions in Australia. Their responses indicate that whereas the participants could explain that Confidence Intervals were used to estimate the value of a population mean, in general they were confused about the theory that enabled probabilities to be assigned to such intervals. Some participants were also confused about the terminology used in inferential statistics. The results of this study suggest that instructors should not underestimate how difficult students find this topic. We must be careful to include questions that require explanations of understanding, not just numerical answers that can be learnt by rote. We conclude that more research is needed into student understanding of confidence intervals, including the suggestion from this study that Confidence Intervals might be considered as a Threshold Concept in advancing students’ statistical thinking.