Research Designs Flashcards
true or false: the only method of control over pre-existing differences is through dispersion.
True
What are major REASONS for choosing a within-subjects design?
- Dispersion; variables are spread equally because they are compared to themselves
- greater statistical power to find small effects
- Convenience (less people needed)
Explain the statistical reason for why you would opt to do a W-S experiment?
Lower Type 2 error (i.e. more likely to reveal a significant difference if a difference does in fact exist)
Maximizes primary variance associated w/ IV & reduces unwanted error variance (NOISE)
When would you choose to not do an W-S experiment and go for between-subjects?
- If conditions cause lasting change; can’t give other levels of the IV because permanent change has happened
- Convenience reasons (lengthier time in session or multiple times)
What are the major threats to the internal validity of a W-S?
All are related to possible effects of repeated testing
Order Effects: response changes in a systematic fashion
Carry Over Effect: when a response to one task/condition varies as a function of whether another task/condition that precedes (or follows) it
A child has to do both a lacing task and puzzle task. By the time the child gets to the puzzle, the performance level starts decreasing. What time of order effect is this? (A THREAT TO INTERNAL VAL.)
Fatigue effect
A child has to do both a clean up task and a reading task. The child did not perform well on the clean up task, but as they got more familiar, their performance increased. What type of order effect is this? (A THREAT TO INTERNAL VALIDITY)
Warm-up effect
A child is presented with a cognitive test that has them do both an inhibitory control test and an attentional span test. Although the child believed that the strategy to the 1st task would be applicable to the 2nd, it was not. What type of threat to internal validity is this?
Carry-Over effect
True or False: There is no general improvement or decline in carry-over effects
True
When are the internal validity threats most likely in W-S experiments?
When researcher adopts a constant order of presentation of conditions
What are the alternatives to a consistent order in administration of conditions?
Randomize (good for when # of tasks/conditions is large)
Counterbalancing (distribute task/condition equiv. across all possible positions)
Which is better counter-balancing or randomizing?
Counterbalancing bc it ensures no confounding of task & order
Permits check of order effects (if ea order is represented enough, we can compare the diff orders of pres)
When would you HAVE TO CHOOSE a between-subjects design?
If expect conditions to cause lasting change.= (e.g. Therapy)
What is the MAJOR THREAT to internal validity in a B-S design?
When the two IV groups have systematically different kinds of participants in them = NON EQUIVALENT GROUPS
What is the selection effects/bias?
When there are already differences found between condition groups; thus not a true effect of experimental manipulations; NOT RANDOMLY DISPERSED
To rule out pre-existing differences between participants in different conditions/groups, the
experimental method of control is through
equal dispersion = meaningful human differences are spread equally across the different conditions/groups.
How do we rule out the non-equivalent groups threat in B-S design?
Random assignment
matching on important attributes
True or False: It’s common for random assignment to be done in combination with a matching constraint (e.g., sex of infant); researchers seldom use totally random assignment.
True
True or False:Most B-S studies include a degree of matching for variables like age and sex; this is a wider attempt to match on all variables of potential importance.
True
What is the logic behind RA?
If ea. person has an equal chance of being selected, then the characteristics associated w/ each person have an equal chance of falling in each group