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.
Flow diagram showing participant enrollment, allocation, and exclusion. Groups shaded in medium gray were included in the slip comparisons (with baseline slips pooled into one group), while groups shaded in light gray were included in the trip comparisons (with baseline trips pooled into one group). Missed slips or trips are described in the text, and resulted in missing data
