Detailed Instructions: Given a text, write a compressed version of it in a single sentence.
Problem:Within-study variation refers to the precision with which a given study estimates the relationship between air quality changes and health effects. Health effects studies provide both a "best estimate" of this relationship plus a measure of the statistical uncertainty of the relationship.
Solution:
Within-study refers to the precision in which a study estimates the relationship between air quality and health effects. Health effects studies provide a "best estimate" plus a measure of the of the relationship.