Table 3.

First bin, intercept point, slope of the log-linear fit model (see Fig. 4), and correlation coefficients for each subject for each device, taking into account the ratio of correct to total responses and the illuminance. The first bin and intercept information shows how the user performed under the optimal condition for viewing on mobile displays: very dark environments. We determine the slopes of the fitted log lines for each subject to be relatively similar, which show that the effect of ambient illumination on user performance degradation is similar even though the devices have differing reflectance coefficients. Because each coefficient is close to −1, we can infer that the ratio of correct to total responses and illuminance are strongly inversely correlated

	Subject 1		Subject 2		Subject 3
Device	A	B	A	B	A	B
Performance first bin	0.860 ± 0.005	0.900 ± 0.004	0.820 ± 0.005	0.860 ± 0.005	0.620 ± 0.009	0.720 ± 0.008
Intercept of fit	0.870 ± 0.014	0.890 ± 0.009	0.860 ± 0.015	0.880 ± 0.008	0.660 ± 0.010	0.740 ± 0.005
y Slope of fit	−0.038 ± 0.003	−0.023 ± 0.001	−0.051 ± 0.003	−0.047 ± 0.014	−0.037 ± 0.010	−0.039 ± 0.005
Correlation coeff.	−0.82	−0.79	−0.75	−0.69	−0.81	−0.83