Research Methods: Experimentation Mr. Koch AP Psychology Andover High School

Psychology uses the scientific method, which consists of three main steps: 1.Formulating a hypothesis 2.Collecting data to support or refute the hypothesis 3.Building a useful theory

Experimental Method An experiment is a method that allows scientists to establish cause and effect. It explores the relationship between the independent variable (IV) and the dependent variable (DV). It begins by establishing operational definitions for the hypothesis. Then it manipulates the experimental condition to test the hypothesis. Experiments also often contain a control condition, in which a control group is exposed to all the same factors as the experimental subjects except the experimental condition.

Experimentation Replication of studies is essential in science. (Other researchers can retest your hypothesis for procedural and outcome validity.) Psychological research should have ecological validity, focusing on processes that occur in real-life environments.

Experimentation A good experiment has reliability and validity. Reliability means the consistency of measurements. (replicable) Validity means the accuracy of measurements.

Experimental Method The experimental method is the most commonly used testing method in psychology because it is accurate and controlled. 1.Hypothesis A specific, testable proposition about something to study » often based on previous research States a relationship between 2 variables (any condition or behavior that can change in quantity/quality) “If – Then” Example: “If students sleep less before the exam, then their grades on the exam will be lower.”

Experimental Method 2. Independent Variable (IV) Controlled and manipulated by the experimenter to determine how it affects the dependent variable (If…) It causes the resulting changes 3. Dependent Variable (DV) Changes in response to the independent variable (Then…) What is being measured It is dependent upon the IV A reduced amount of sleep will result in lower test scores among students. (IV)(DV)

Experimental Method 4. Random Assignment Each variable has an equal chance of being selected – “Random assignment” vs. “Random Sample” 5. Preselected or Stratified Sample The experimenter specifically selects a demographic for the study (i.e. toddlers, AP students, men, women, etc.) 6. Experimental Group (Condition) The group in which the condition under study is present 7. Control Group (Condition) Altered condition is not present – baseline for comparison

Experimental Method 8. Controlled Variable Any variable that is held constant among all subjects – Reduces possibility of alternative explanations 9. Confounding Variable Any variable that is not controlled and could possibly affect the validity of the results 10. Theory A general principle based on information to explain what is learned – Can be retested for validity 11. Subject The organism participating in the experiment – Subject responses = dependent variable

Experimentation Additional terms: – Placebo Effect Experimental results caused by participant’s expectations, rather than actual treatment/condition – Single-blind design Study in which participant is unaware of placement in experimental or control group – Experimenter Bias Unintentional effects experimenters may exert on their results – Double-blind design Study in which neither the experimenter nor the participant knows if the subject is in the experimental or control group

Experimenter Bias?...

Ethics Because psychologists have an ethical obligation to protect the dignity and welfare of the people who participate in research, the APA has drawn up a set of ethical principles to guide research. The code sets up 4 main conditions aimed at ensuring subjects’: 1.Privacy 2.Voluntary participation 3.Informed consent 4.Freedom from harm Researchers must also follow federal regulations and guidelines of local institutional review boards. Research that cannot ethically be done with humans can sometimes be performed on animals.

Ethics Advantages to Animal Testing: 1.Physiology is often similar to humans 2.Behavior of animals can be more controlled than humans (i.e. rats can be raised in cages) 3.Short life spans – behavior of many generations can be studied in a short time period 4.Drug testing or surgery (brain)

Ethics APA Guidelines for Animal Subjects 1.Acquired and treated according to local laws 2.Comfortable environment (unless absolutely necessary for testing procedure) – Any pain/discomfort/stress must be justified by expected benefits to human/animal welfare 3.Use must be directed by qualified researcher (must possess a master’s degree or greater in psychology)