Fig. 3.

The minimum value required for the joint minimum strength of association of the risk ratio scale for an unmeasured confounder with the CTD-ILD and ILD-only groups to fully explain an observed treatment–outcome risk ratio of RR = 2.28 in the 40 to 49 years old age group. The E-value essentially sets the 2 parameters (RR_UD and RR_EU) equal to each other to determine the required minimum for both values. The E-value estimate corresponds to the point (3.60, 3.60) in the 40 to 49 years old age group. RR, relative risk; E, exposure; U, unmeasured cofounder; D, outcome; RR_EU, maximum risk ratio for any specific level of the unmeasured confounders comparing the lung cancer incidence between the CTD-ILD and ILD-only; RR_UD, maximum risk ratio for the outcome when comparing any 2 categories of the unmeasured confounders; CTD-ILD, connective tissue disease-associated interstitial lung disease; ILD-only, interstitial lung disease