Deciding which medical treatments work better than others is a tough job, but health policy experts say it could help hold down health care costs. Still, Americans aren't too sure they want the government deciding which treatments their insurance should pay for, according to a new poll conducted by NPR, the Kaiser Family Foundation and the Harvard School of Public Health.

More than half of Americans polled said they would trust an independent scientific panel to make decisions about which medical treatments insurers could cover. Yet only 42 percent said they would trust a government health agency to do the same job.

The government stimulus package includes $1 billion to conduct comparative effectiveness research, which would carefully study the different types of medical treatment to determine what works best. The Obama administration has been soliciting the advice of health experts and the public on how it should be done, and who should have the final word.

Right now, there are no national standards for what health insurance contracts are required to cover.

Some say decisions about comparative effectiveness can be left to the marketplace. Insurance companies could make it clear what they would and would not pay for, and people could decide between policies.

Some of that is already going on, says Grace-Marie Turner, president of the Galen Institute, a nonprofit institute that promotes free-market solutions. "We have lots of companies now that are doing a lot of work to decide what treatments have value, and what don't."

But other health policy experts say it will take a government body or an independent board to really determine what works and what doesn't. A government board could handle it, says health economist Uwe Reinhardt of Princeton University, but an independent board might be more acceptable to the public.

What's important, Reinhardt says, is that something gets done soon. "The idea that every American has the right to everything imaginable—whether it's been shown to work or not—is just tragic," he says. "Ultimately that leads to what we've had, where health spending grows 2.5 percentage points faster than the rest of the GDP. For the last 40 years we've had this."

He says if we continue on this path, in 2050 we'll be spending 40 percent of the GDP on health care.