Skip to main content
Figure 3 | BMC Medical Research Methodology

Figure 3

From: Bias in trials comparing paired continuous tests can cause researchers to choose the wrong screening modality

Figure 3

True and observed ROC curves for a hypothetical example where bias did not change the scientific conclusion. The parameters for this example were chosen to illustrate a case where paired screening trial bias did not change the direction of the difference in AUC, nor the scientific conclusion. The chance of recall for either screening test for a participant who had disease was 8%. For this example, we fixed the disease rate, r = 0.01; the chance that participants with disease would experience signs and symptoms within the year of follow-up, ψ = 0.1; the variance, σ 2 = 1. The means of the distributions of test results for cases for Test 1 and Test 2 were 1.1 and 1.1, respectively, and the means for non-cases for Test 1 and Test 2 were 1.6 and 0.35. The correlation between test scores for cases was fixed at 0.1, as was the correlation for non-cases. All test scores above 2.5 on either test, or participants who had signs or symptoms had an infallible secondary test to determine disease status. For participants with scores below 2.5 on both tests, a less sensitive method was used to approximate disease status.

Back to article page