They relied on volunteers who most likely were not representative of the general population.

Usually, they are not funded by the government, but instead rely on their own resources and volunteers.

Guys are taking on volunteers and paying them out of their own pockets.

This effort has not been funded so far and relies only on volunteers.

We tested the effects on volunteers during the design stages.

It relies on volunteers, who mostly have a strong interest in the welfare of others.

For now, we'll have to rely mostly on contributions and volunteers.

"You can see why we didn't want to test them even on volunteers."

A clinical trial is a research study on human volunteers designed to answer specific health questions.

It runs on local volunteers who give a piece of their time to help others.