Does regular exercise reduce bone loss in postmenopausal wom
     Does regular exercise reduce bone loss in post-menopausal women? Here are two ways to study this question. Explain clearly w y the second design will produce more trustworthy data.  A researcher finds 1000 postmenopausal women who exercise regularly. She matches each with a similar postmenopausal woman who does not exercise regularly, and she follows both groups for 5 years.  Another researcher finds 2000 postmenopausal women who are willing to participate in a study. She assigns 1000 of the women to a regular program of supervised exercise. The other 1000 continue their usual habits. The researcher follows both groups for 5 years. 
  
  Solution
From the given designs second design will produce trustworthy data because she regularly supervised exercised.

