1. Introduction to Experimental Design
Sections 3
Introduction to
Experimental
Design

2. Definitions treatment – the property being studied
treatment group – the group possessing the property
control group – the group not possessing the property

3. Definitions continued
confounding factors – properties other than the treatment that can influence a study

4. observational study
the researcher does not control which subjects are assigned to the treatment
observations and measurements of individuals are conducted in a way that doesn’t change the variable being measured

5. controlled experiment
the researcher can control which subjects are assigned to the treatment
a treatment is deliberately imposed on individuals in order to observe a possible change in the variable being measured

6. Types of studies
cross-sectional study - different subjects are compared to one another at the same point in time
longitudinal study -the same subjects are compared to themselves at different points in time

7. A researcher is attempting to measure the effectiveness of a new drug that claims to lessen the severity of heart attacks. Half of the study participants are given the drug and the remainder are given a placebo.

8. 1.) Does the study depict a controlled experiment or an observational study? 2.) What is the treatment? 3.) What is the treatment group? 4.) What is the control group? 5.) Name a confounding factor that could influence the study.

9. Determine whether the study depicts an observational study or a controlled experiment.
1. A study to determine whether there is a relationship between the rate of cancer and an individual’s proximity to high-tension wires.
2. Rats with cancer are divided into two groups. One group receives 5 mg of an experimental drug that is thought to fight cancer, and the other receives 10 mg. After two years, the spread of cancer is measured.

10. Determine whether the study depicts an observational study or a controlled experiment.
3. While shopping, 200 people are asked toperform a taste test in which they drink from two unmarked cups. They are then asked which drink they prefer.
4. A survey is conducted asking 400 people, “Do you prefer Coke or Pepsi?”