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PNB 3RM3 Unit 3 (Single Factor Design (1IV & 1DV) (Between Groups…
PNB 3RM3 Unit 3
Single Factor Design (1IV & 1DV)
Between Groups Design
Advantages
1.
No Carry-Over Effects
for participants
No need to create equivalent versions of the same task
Low concern for revealing your hypothesis
Disadvantages
Lack of Equivalent Groups
Uses A LOT of Resources
When to Use
Your research question demands separate groups
Your experiment is too demanding for within groups
It makes sense and you like it
Assigning Participants to Conditions
Independent groups design (
Random Assignment)
Advantage
: Every participant has an equal chance of placement
Disadvantage
: Not COMPLETELY Equivalent (b/c laws of chance- chance one group may have one type of participant)
Solutions To Disadvantages
1. Safety in Numbers
(lots of participants, 30 per IV)
2. Block Randomization
Matched Groups
Design (Pretesting for a deviate, then assigning to a condition)
Advantage
: Gives even groups
Disadvantages
Impractical
: you have to pre-test
Hinting at Hypothesis
- Solution = running a standardized test
Natural Groups
Design : Use
subject variables
to assign participants
Advantage
: good for testing Subject variable as IV (Ex. gender)
Within Groups Design
Advantages
Require
Fewer Participants
to obtain the same data per condition
Equivalent Groups
: same participants, don't need to control for individual differences
Other Advantages:
Resource sparing benefits, special populations with low participant pool, only way of answering quesiton
Disadvantages
High concern for figuring out
hypothesis
Attrition
: when participants leave mid-experiment
Selective attrition
- very bad, people leaving due to treatment condition/experimental design
Order Effects
: when order of IV conditions affect your DV
Progressive Effects
: First treatment affects DV on Second treatment (Produces a
CONFOUND
)
Practice Effects
: Performance improves as a result of previous exposure to conditions
Carry-Over Effect
: Response in one condition is uniquely influenced by responses in previous conditions
Solution to order effects:
Counterbalancing
- changing the levels of exposure of your IV so no level has an advantage or disadvantage over other levels; makes effects
extraneous
rather than
confounding
Exposure to Levels of
IV once
Complete Counter Balancing
Advantage:: takes into account
all possible confounding factors
Disadvantages
High number of orders
: you need
n! orders
(more than 4 levels of an IV is not feasible)
Not feasible
: recruiting/running a number of participants over many levels
Latin Square
(Partial Counterbalancing): 3x3 matrix filling in missing items of conditions for participants
Advantage
: Not as extensive or time consuming as complete counterbalancing
Disadvantage
: Doesn't COMPLETELY counterbalance
Random Selected Orders
: Create a bunch of different orders, randomly select the set of orders for the participant
Exposure to Levels of
IV 2 or more times
Block Randomization
Reverse Counter Balancing
Disadvantage:
fatiguing participants
Ways of Measuring a
DV
Concurrent-Measures Design
: testing
all levels of the IV
at once, then measuring the
DV
Repeated-Measures Design
: Testing the
IV
, then
DV
, then
DV
again ; Participants experience different levels of the IV in different orders