FIG. 1.

FPRs for various software scenarios in AFNI, with 1000 two-sample 3D t-tests [as in Eklund and associates (2015, 2016)] using 20 subjects' data in each sample. “Buggy” (A–C) and “fixed” (D–F) mean that the cluster-size thresholds were selected using the Gaussian shape model with the FWHM being the median of the 40 individual subject values: “buggy” and “fixed” via 3dClustSim before and after the bug fix, respectively. “Mixed ACF” (G–I) means that the cluster-size threshold was selected using Eq. (3) for spatial correlation of the noise, with the a,b,c parameters being the median of the 40 individual subject's values (estimated via program 3dFWHMx). Three different voxelwise p value thresholds [one-sided tests, as used in Eklund and associates (2016)] are shown. The black line shows the nominal 5% FPR (out of 1000 trials), and the gray band shows its theoretical 95% confidence interval, 3.6–6.4%. As in ENK16, different smoothing values were tested (4–10 mm). B1 = 10-sec block; B2 = 30-sec block; E1 = regular event related; E2 = randomized event related. ACF, autocorrelation function; FPR, false-positive rate; FWHM, full-width at half-maximum.