Classify the following studies as descriptive or inferential and explain your reasons:

a. A study on stress concluded that more than half of all Americans older than 18 have at least "moderate" stress in their lives. The study was based on responses of 34,000 households to the 1985 National Health Interview Survey.

b. A report in a farming magazine indicates that more than 95% of the 400 largest farms in the nation are still considered family operations.