Figure 3.
Absolute standardized differences of all covariables before and after matching between the theophylline and control groups. FEV1, forced expiratory volume in 1 second; COPD, chronic obstructive pulmonary disease
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.