Classify each description as either an observational study or an experiment.

In a sleep study designed to test whether a new supplement helps individuals sleep longer, a computer randomly assigns each participant either to a group receiving the supplement or to a group receiving an inactive pill.

A political scientist seeks to determine if women between the ages of 25 and 30 are more likely than men of the same age to vote for a Democratic candidate. The scientist selects a sample of voters from this age group to survey their political preference.

Agricultural scientists seek to test the effects of a new pesticide on corn crops. Half of the participating farmers are assigned the new pesticide and the other half continue using an alternative pesticide. The crops are compared after two seasons.

Students from 10 schools are divided into groups by researchers, those that participate in musical activities and those that do not. Student grades are monitored for a year to determine if those who participate in musical activities achieve higher grades.

A cancer study began by surveying male patients between the ages of 35 and 55 at a local hospital about their exercise routine. The health of these men is tracked over 10 years to determine the effect of exercise on lowering the risk of cancer.

Researchers studying how exercise affects cholesterol sample 50 people who exercise regularly and 50 who do not. Blood was drawn from each person and serum cholesterol was measured.

An observational study is a study where researchers simply collect data based on what is observed and give results based on the data collected.
There is no control over the variables in an observational study.
An experiment is a method of applying treatments to a group and recording the effects.
The variables in a an experiment can be controlled.
An observational study is where nothing changes but in an experimental study we have control over groups and may change.

1. This is an experiment as people were divided into groups and treatment were given.

2. This is an observational study as no treatment was done on the people just political preference was measured on the basis of collected data.

3. This is an experiment as farmers were divided into groups and effects of a new pesticide was tested.

4. This is an observational study as the data collected told about effect of exercise on lowering the risk of cancer and no experiments were carried out.

5. This is an experiment as people were divided into groups and cholesterol was measured with and without exercise.