Chapter 9.5, Problem 13MS

Stressful diet. One hundred young women were given a diet survey and were classified as having either a healthy diet or an unhealthy diet. Each was then given a questionnaire designed to assess her degree of stress. It was found that those in the healthy diet group tended to have significantly lower levels of stress than those in the unhealthy diet group. Is this good evidence that a healthy diet causes lower stress levels?