Experimental Psychology Quiz #2

Sample

Any group from which information is obtained

Generalizability

The extent to which the sample represents the population (2 types)

Population Generalizability

the degree to which a sample represents the population of interest

Ecological Generalizability

the extent to which the results of a study can be generalized to conditions or settings other than those that prevailed in the study

Random sampling

a method of selecting participants from a population by chance so that biases do not alter the sample

Nonrandom sampling

a method in which each member of the population does not have an equal chance of being selected

What matters most for external validity?

sampling technique, not sample size, determines external validity

Reliability

the degree to which the particular way researchers measure a given variable is likely to yield consistent results (internal consistency)

What 2 factors determine Cronbach’s alpha?

1. number of items—as number increases, Cronbach’s alpha increases

2. average item intercorrelation—as the average item intercorrelation increases, Cronbach’s alpha increases

Ratings of Cronbach’s alpha

Validity

a study measures what it claims to measure

Reliability vs. Validity

A scale CAN be reliable but not valid; it CANNOT be an unreliable scale and be valid!

i. Reliability is a necessary precondition for validity

ii. Validity is NOT a necessary precondition for reliability

4 big types of validity

Construct, External, Statistical, Internal

Construct Validity

how well the variables in a study are measured or manipulated; the extent to which the variables in a study are a good approximation of the conceptual variables

External Validity

the extent to which the results of a study generalize to some larger population, as well as to other times or situations

Statistical Validity

how well the numbers support the claim

Internal Validity

In a relationship between one variable (A) and another variable (B), the extent to which A, rather than some other variable (C), is responsible for changes in B

5 types of Construct Validity

Face, content, criterion, convergent, discriminant

Face Validity

it looks like what you want it to measure

Content Validity

the measure contains all the parts that your theory says it should contain

Criterion Validity

your measure is correlated with a relevant behavioral outcome

Convergent Validity

your self-report measure is more strongly associated with self-report measures of similar constructs

Discriminant Validity

your self-report measure is less strongly associated with self-report measures of dissimilar constructs

Type of instruments

norm-referenced, criterion-referenced

Norm-referenced Instrument

Based on some index of test-takers’ scores; typically expressed as percentiles

Criterion-referenced instrument

scores compared to a desired level of aptitude; example—solved at least 75% of the assigned problems