1. Methodological Evaluation of Experiments
By Mr Daniel Hansson

2. Important Concepts Reliability Replicability Validity
Ecological validity
External validity
Internal validity
Confounding & Extraneous variables
Control

3. Reliability
Reliability: The extent to which an experiment yields the same result over repeated trials
Replicability: The ability of a test to be easily replicated

4. Questions
How reliable would you say that the results of your study were?
How standardized were the procedures of the study? Is the study easily replicated?

5. Validity
Validity: Whether you measure what you are supposed to measure
Ecological validity: The extent to which research findings can be applied to real life
External validity: The extent to which a research finding can be generalized to persons, settings, or times other than those that were the subject of study.

6. Validity Activity
1. Take the IQ test at How valid do you think that the results were? Motivate your answer.
2. How well do you think that the results of your study could be generalized to people of other age groups or from other cultures?
3. Do you think the results of your study can be applied to real life situations?

7. Internal Validity
Internal validity: Whether there were confounding/extraneous variables that attributed to the results
Confounding/extraneous variables: Variables other than the independent variable that may affect the independent variable. Confounding variables are variables related to the design of the experiment, extraneous variables are usually related to participants
Control: A variable in the experiment that is kept constant (the same) for all participants to improve internal validity. E.g. Same treatment, same/clear instructions, same gender, same age

8. Examples of Confounding Variables
Experimenter effect: Researcher’s bias may cause them to unconsciously influence the participants of the experiment
Demand characteristics: When participants form an interpretation of the experiment’s purpose and unconsciously change their behavior accordingly

9. Questions What were the controls in your experiment?
Think of all the possible confounding variables that could have affected the internal validity of your experiment