1. Research Methods
Chapter 2

2. Reasoning Fallacies
Hindsight bias – tendency to believe, after learning an outcome, that we would have foreseen it
The “I knew it all along” phenomenon

3. Psychology as Science
Empiricism – belief that accurate knowledge of the world requires observation of it
Limitations of casual observation:
Unstable
Can’t tell us about the properties we might be interested in

4. Psychology as a Science -cont-
So we must use measurement to:
Define the property we want to measure in concrete terms
Operational definition – description of procedures used to define research variables
Ex: human intelligence may be operationally defined as what an intelligence test measures

5. Psychology as a Science -cont-
A good measurement has
Validity – allows one to draw accurate inferences from it
Replication– produces the same result whenever it is used to measure the same thing

6. Case study
Studying a single individual in depth

7. Naturalistic observation
Unobtrusively observing people in their natural environment
Avoid demand characteristics – aspects that cause people to behave as they think an observer wants/expects them to behave
Limitations:
Some things psychologists want to observe don’t occur naturally
Some things can only be gathered from direct observation with a person

8. Survey
Survey - uses a representative sample of people to estimate attitudes or reported behaviors of a whole population
Limitation:
Respondents may not answer honestly

9. Survey -cont-
Population - all the cases in a group being studied from which samples may be drawn
Random sample - every member of a population has an equal chance of inclusion

10. Correlational Studies
Correlation – the “co-relationship” or pattern of co- variation between two variables
Positive – two sets of variables go up or down together
Negative – two sets of variables relate inversely

11. Correlation vs. Causation
Third-variable correlation – two variables may be correlated only because they are both caused by a third variable
Correlation does not prove causation

12. Correlation -cont-
Illusory correlation: The perception of a relationship where none exists

13. Experimentation
Used to establish the casual relationship between variables
Independent variable – variable that is manipulated
Is “independent” of what the participant says/does
Dependent variable – variable that is measured
“Depends” on what the participant says or does
Control group – group that does not receive the treatment
Experimental group – group does receive the treatment

14. Experimentation -cont-
An experiment is internally valid when:
An independent variable has been effectively manipulated
A dependent variable has been measured in an unbiased way with a valid, powerful, and reliable measure
A correlation has been observed between the independent and the dependent variable
External validity – property of an experiment in which the IV and DV is operationally defined in a normal, typical, or realistic way

15. Experimentation -cont-
It is generally not feasible to use a random sample when conducting an experiment
Experiments utilize
Random assignment - assigning participants to experimental and control groups by chance
Double blind procedure - neither the research participants nor the research staff know if participants received the treatment or a placebo - sugar pill
Eliminates placebo effect - experimental results caused by expectations alone

16. Measures of Central Tendency
Mean – sum of a set of scores in a distribution divided by the number of scores
Extreme scores have a greater impact on the mean than on the mode or median
Median – score that divides a frequency distribution exactly in half, so that the same number of scores lie on each side of it
Mode – the most frequently occurring score in a distribution

17. Measures of Variation
Definition – a single score that presents information about the spread of scores in a distribution
Range – the highest score in a distribution minus the lowest score
Standard deviation – a standard measurement of how much the scores in a distribution deviate from the mean

18. Normal distribution Form a bell-shaped curve
In a normal distribution of test scores, 50% of scores fall at or above the mean score and 50% of scores fall at or below the mean score
Approximately 1/3 of the scores fall one standard deviation below the mean and 1/3 fall one standard deviation above the mean

19. All score-based normal curves have the following 68-95-99
All score-based normal curves have the following rule in common:
Approximately 68% of all scores fall within one standard deviation of the mean
Approximately 95% fall within two standard deviations of the mean
Approximately 99.7% fall within three standard deviations of the mean

20. Skewed distributions
Positively skewed distributions have more scores on the low end of the scale
The median is the best representation of central tendency
Negatively skewed distributions have more scores on the high end of the scale
The median is a better representative of central tendency

22. Ethics
Obtain informed consent – written agreement to participate in a study made by an adult who has been informed of all the risks participation may entail
Participation may not be coerced
Psychologists must protect participants from physical or psychological harm
Risk of embarrassment or minor pain must be outweighed by social benefits of new knowledge gained by study
Must provide a debriefing – verbal description of true nature and purpose of study