Fed Chair Janet Yellen has made clear she would rather delay an interest rate hike for too long than move sooner and risk jeopardizing a tepid economic recovery, a conviction that will face its sharpest test yet on Thursday. A rate hike would be the first in the United States in nearly a decade. Fed watchers, however, see the outcome as a toss-up, with Yellen’s consistently stated desire to see workers reap more benefits from the recovery, coupled with weak price rises and a variety of global risks, looming large.