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A set of 3510 screening cases read as part of a national screening program by 10 qualified radiologist readers forms the basis for our study. The readers give a suspicion score (on a standalone device) in addition to their standard screening report. The score is time-stamped so that reading order and batch grouping can be assessed. Batches are defined as groups of cases with less than 10 minutes (600 s) between sequential readings. We use Kendall’s Tau, weighted by batch size, as a measure of association between batch position, and suspicion score or reading time. Randomization is used to get confidence intervals on the null hypothesis ( τ=0 ). We find significant associations between batch position and both of the variables under investigation (suspicion scores and reading time). The associations are negative, suggesting that both suspicion and reading time are reduced at later points in a batch. These results are consistent with the hypothesis that readers are becoming visually adapted to the properties of the images as they progress through a batch of cases, affecting their perception and decisions about the images. |
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