Determine if the study is an observational study or an experimental design

1. A political pollster reports his candidate has a 6% lead in the poll with 4% undecided. ____________________
2. A quality control specialist compares the output from a machine with new lubricant with the output of machines with the old lubricant . ____________________

Determine if the study suffers from selection bias, participation bias, both or neither.

1. "68% of adults in United States regularly visit a hospital". This result was reached after an individual randomly selected 250 members of her retirement home. ___________________
2. You are interested in the degree of satisfaction of customers at a local restaurant. For one month you leave a customer satisfaction survey on every table and ask customers to fill it out and place in a box before they leave. ____________________
3. As voters left polling stations across the county, every 100^th voter from each location was asked who they chose to be mayor. ____________________