confound: uncontrolled extraneous variable that could provide an alternative explanation

Social desirability bias - when people respond by trying to put themselves in a favorable light

UNOBTRUSIVE and ARCHIVAL MEASURES:

physical trace studies - using physical remnants, fragments, products as evidence of past behavior

erosion (wearing down)

accretion (building up)

archival study - examines already existing records (the experimenter is not collecting new data, but examining data already gathered by someone else).

cross sectional design - one "slice" of time

successive independent samples - different groups measured at different times.

longitudinal design - same group followed over time.

cohort - a group of people exposed to the same set of circumstances (especially a group born at the same time).

cohort effect - effect that is due to the circumstances a group of people are exposed to (and often not the variables of interest).

Ex: Vietnam veterans may score differently on a "startle reaction" test because of combat experiences.

OR

People who lived through the "energy crisis" in the 1970's may be more concerned about conserving energy.

respondant [subject] mortality - the loss of subjects in a study because they drop out, disappear, or die.

Between subjects design--

different groups of subjects serve in the different conditions of the study

Within subjects design--

the same group of subjects experiences the different conditions in the study

Within-subjects advantages:

1) Fewer subjects

2) Less admininstrative work

3) Reduces unwanted error variance between subjects

Ways to deal with practice effects

1) Every possible order

(complete counterbalancing)

2) Rotate order

3) Latin square

(partial counterbalancing)

Ex. of Latin square (subjects exposed to 4 different kinds of music):

 
                cheerful, sad, romantic, patriotic
                sad, patriotic, cheerful, romantic
                patriotic, romantic, sad, cheerful
                romantic, cheerful, patriotic, sad

Repeating conditions in within subjects designs:

1) ABBA (reverse counterbalancing)

ABBA order--When subjects experience conditions more than once, they first experience the conditions in one order, and then the reverse order.

Ex:

Diet Coke

Diet Pepsi

Diet Safeway Select Cola

Diet Safeway Select Cola

Diet Pepsi

Diet Coke

2) block randomization

Block Randomization -- counterbalancing technique to insure that when subjects are tested in each condition more than once, they experience each condition once before experiencing a condition again.

Block randomization is also used in BETWEEN subjects designs--

assures that one subject experiences each condition before a second subject is run again in that condition.


Assigning subjects to conditions in between subjects designs:
- random assignment
- block randomization
- matched groups