Definition of between-participants designs?
- participants are assigned to one condition only
- comparison between different groups
- also known as independent measures/non-repeated measures
When is between-participants design used?
- when IV is an individual differences variable
- when experience gained from participating in one condition makes it impossible to participate in another
Advantages of between-participants design?
- each participant is fresh and naive to the hypothesis
- maintains validity
Disadvantages of between-participants design?
- more participants need to be recruited
- may be unexpected differences between groups of participants
Ways to create equivalent groups?
- random assignment
- matching procedure (followed by random assignment)
What is random assignment?
- every participant has equal chance of being placed in any of the conditions
- objective is to spread individual differences evenly
What is blocked random assignment?
- equal chance of being placed in any condition
- ensures each condition has participant before any other condition is repeated
- makes sure one group doesn’t have all of a certain type of person in it
- labels participants with which version of the problematic characteristic they are
What is matching procedure?
- get scores for each person on the matching variable
- arrange scores in ascending order
- create pairs of scores where each has adjacent scores (e.g. highest one goes with the lowest one till all are paired)
What conditions are needed for matching procedures?
- need reason to believe matching variable will have predictable effect on DV
- must be logical,accurate way of measuring the matching variable
- look at existing literature to identify those variables
- take into account whether it’s practical to use the procedure
Definition of within-participants design?
- participants take part in 2 or more conditions
- comparison within the same group
- also known as repeated measures/within-subjects
When is within-participants design used?
- when conditions require brief time to test but extensive preparation
- when population of interest is small
Advantages of within-participants design?
- more data from each participant
- can recruit fewer
- reduced error variance
Disadvantages of within-participants design?
- threats to internal validity
- order effects
What are order effects?
- practice effect
- fatigue effect
- carryover effect
Definition of practice effect?
-performance on later trials is improved due to practice
Definition of fatigue effect?
- performance on later trials is reduced due to fatigue
- physical or psychological
Definition of carryover effect?
-one sequence of conditions produces different results than another sequence
How can you control order effects?
-the use of counterbalancing
Definition of counterbalancing?
-using more than one sequence of conditions
Definition of complete counterbalancing?
-every possible sequence is used at least once
Definition of partial counterbalancing?
-using subset of total number of sequences
Definition of experimenter bias?
-experimenter is aware of how each group of participants is being treated, which conditions they belong to
How to reduce experimenter bias?
- automate procedure
- double-blind procedure
Definition of automate procedure?
-systematically every participant is then treated the same way
