Which of the following explains how the economic value of forest ecosystems is measured? 1. by measuring the total value of recreation money made from forests
2. by measuring the total value of raw materials taken directly from forests
3. by measuring the total value of services and goods that are taken from forests
4. by measuring the total value of products made from Items exported from forests

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.