A corporation has developed a new thirty-minute exercise program that can be taken in the gym in its building. The company would like to study whether an employee's productivity could be improved by getting them to do the program. They hire a statistician to help them with this.

The company has five departments. The statistician decides to get 30 employees from each department. For each group of 30, 15 are randomly chosen to take part in the exercise program for one month. The other 15 are left to go about their lives normally. The productivity for each of the 150 employees is recorded at the end of the month.

From the information given the above study is most accurately described as:

1) an observational study that does not make use of a stratified sample

2) an observational study that makes use of a stratified sample

3) an experiment that does not make use of blocking or blinding

4) an experiment that makes use of blocking an experiment that makes use of blinding