Ch 2

Theory

A general statement about the relationship between constructs or events.

• Personality researchers work with theories narrower in application

  • e.g., speculating about the reasons why some people are more motivated to achieve than others or the relationship between a parent's behaviour and a child's level of self esteem

• Theories themselves are never tested

Hypothesis

A formal prediction about the relationship between two or more variables that is logically derived from a theory.

• Hypotheses are derived from theories that can then be tested in research

Characteristics of a good theory

1. parsimony

2. a good theory is useful

Parsimony

The simplest theory that can explain a phenomenon is preferred.

A good theory is useful

A theory must generate testable hypotheses to be valuable to scientists; untestable ideas lack scientific investigation.

Independent Variable (IV)

The variable that determines how the groups in the experiment are divided; it is manipulated by the experimenter.

• uses different levels of the IV to create the experimental groups

Dependent Variable (DV)

The variable that is measured by the investigator and used to compare the experimental groups.

• Differences between groups on the DV can be attributed to the different levels of the IV

Interaction between factors

• How one IV affects the DV Is dependent on IV

e.g., e.g., whether anxiety (IV) leads to an increase or decrease in questions (DV) is dependent on whether the participant is high or low in shyness (IV)

Manipulated Independent Variable

An independent variable that is altered by the researcher to examine its effects.

• begins with a large number of participants and randomly assigns them to experimental groups

• Individual differences are accounted for with the law of large numbers

Nonmanipulated Independent Variable

An independent variable that exists without researchers' intervention.

• e.g., splitting a group into first-born, second-born, and third-born children

• Each participant already belonged to one of the groups, and the researchers simply determined which group that was

The problem with nonmanipulated IVs?

• The researcher cannot assume the groups are nearly identical at the beginning of the experiment (non-equivalent groups)

• Therefore, difference could be attributed to individual differences and not the IV

Replication

The process of repeating a study to determine the strength and reliability of an effect.

• It is dangerous to assume that a significant finding from one study provides reliable evidence for an effect

• The more often an effect is found in research, the more confidence we have that it reflects a genuine relationship

Case Study Method

An in-depth evaluation of a single individual, often during a specific problem of interest.

• usually descriptive

Weaknesses to case studies

1. It is difficult to generalize from a single individual to other people

   Just because one person reacts to events a certain way, does not mean other people do

2. It is difficult to determine a cause-and-effect relationship with the case study method

3. The accuracy of some case study observations is questionable

• Researchers form expectations --> causes them to see what confirms their hypotheses --> overlook disconfirming evidence

Why use case studies?

1. Other research methods might not do the job

• Quantitative methods may not capture the richness of a person's life

2. Valuable for generating hypotheses about the nature of human personality

3. Useful for rare cases

4. Appropriate when researchers can argue that the individual being studied is essentially no different from all normal participants on the dimension of interest

5. Illustrate a treatment

6. Demonstrate possibilities (I.e., high ends of the spectrum/exceptions)

Statistical significance

• If the difference is so large that in all likelihood, it was not caused by chance but reflects a true difference, the difference is statistically significant

• If the difference between the scores is so large that it would occur less than 5% of the time by chance, the difference is probably genuine

Reliability

The extent to which a test measures consistently over time.

• A test has good reliability when it measures consistently

• But since we assume personality is relatively consistent over time, tests designed to measure personality should provide consistent scores

test-retest reliability coefficiant

• Large group takes a test --> weeks later, they take the test again --> correlation coefficient is calculated between the 2 scores

  •  A high correlation coefficient indicates good consistency over time

Internal consistency

• A test is internally consistent when all items on the test measure the same thing

Validity

The extent to which a test measures what it is designed to measure.

Face Validity

The extent to which a test appears to measure what it is intended to measure.

Congruent/Convergent Validity

The extent to which scores from a test correlate with other measures of the same construct.

Discriminant Validity

The extent to which a test score does not correlate with scores of theoretically unrelated measures.

Behavioral Validation

The test scores predict relevant behavior in practical situations.

• It is possible to demonstrate a tests face validity, congruent validity, and discriminant validity, yet still not have a valid measure if unable to predict how people would act in relevant situations.

Hypothetical constructs

inventions researchers employ to describe concepts that have no physical reality

• e.g., intelligence

• attempts to quantify a person's mental capability across different domains.