Experimental Designs, Chapter 6, 3 Flashcards
What are experimental designs?
The different ways in which participants can be organised in relation to the experimental conditions
What is independent groups design?
Participants are allocated to different groups where each group represents one experimental condition
What are repeated measures?
All participants take part in all conditions of the experiment
What is matched pairs design?
Pairs of participants are first matched on some variables that may affect the dependent variable. Then one member of the pair is assigned to Condition A and the other to Condition B
What is random allocation?
An attempt to control for participant variables in an independent groups design which ensures that each participant has the same chance of being in one condition as any other
What is counterbalancing?
An attempt to control for the effects of order in a repeated measures design: half the participants experience the conditions in one order and the other half in the opposite order
How would independent groups be incorporated in the energy drink investigation?
One group of participants (Group 1) drinking the energy drink (Condition A, the experimental condition)
A different group of participants (Group 2) drinking water (Condition A ) the control experiment
How would we compare the performance of the two groups in the energy drink investigation?
Compare the difference in the mean number of words spoken in the five-minute period after drinking for each group/ condition
How would repeated measures be incorporated in the energy drink investigation?
Each participant would first experience Condition A (the energy drink condition, the experimental condition)
Each participant would then later be tested again in Condition B (the glass of water condition, the control condition)
What would be completed in the energy drink investigation to see if there was a difference between the repeated measures in both conditions?
The two mean scores from both conditions would be compared to see if there was a difference
What is an example of a matched pairs design?
In a memory study, participants might be matched on their IQ, as this is a good indicator on their ability to recall information
How would a memory study in a matched pairs design play out?
The two participants with the first and second highest IQ would be paired together as would the participants with the third and fourth highest, etc.
One participant from each pair would be allocated to a different condition of the experiment
What is the matched pairs design in a memory study an attempt to control?
An attempt to control for the confounding variable of participant variables and often necessitates the use of a pre-test if matching is to be effective
What is the biggest issue with an independent groups design?
The participants who occupy the different groups are not the same in terms of participant variables
What is an example of the matched pairs design in the energy drink investigation?
We might observe participants interacting in a room before the experiment begins and select the two people that appear to be the chattiest.
One of the pair would be placed in condition A and the other in condition B.
We would then do the same with the third and fourth most talkative participants, etc.
The experiment would then be run in the same way as an independent groups design
What may be more to do with participant variables than the effects of the IV?
If a researcher finds a mean difference between the groups on the dependent variable
What may the mean difference between the groups on the dependent variable act as?
A confounding variable, reducing the validity of the findings
To deal with this problem of a confounding variable in the mean difference between the groups on the dependent variable, what do researcher’s use?
Random allocation
What are independent groups less of ?
Independent groups are less economical than repeated measures as each participant contributes a single result only
How many participants would be needed in an independent groups designs compared to a repeated measures design?
Twice as many participants would be needed to produce equivalent data to that collected in a repeated measures design?
What is wrong with independent groups designs needed twice as many participants?
This increases the the time/ money spent on recruiting participants
What are the strengths of using independent groups?
Order effects are not a problem whereas they are a problem for repeated measures designs. Participants are also less likely to guess the aims
What is the biggest issue for repeated measures?
Each participant has to do at least 2 tasks and the order of these tasks may be significant (i.e. there are order effects)
Why may having an energy drink first be an order effect?
They may have a continuing effect when a participant drinks water afterwards. To deal with this researchers use counterbalancing
How do researches deal with order effects?
By using counterbalancing
What can order effects also arise from?
Because repeating two tasks could create boredom or fatigue that might cause deterioration in performance on the second task, so it matters what orders tasks are in
Alternatively, how might the participants’ performance improve?
Through effects of practice, especially on a skill-based task- in this case of the energy drinks, participants would perform better on the second task
What does order act as in the energy drink experiment?
As a confounding variable
What is also more likely when participants experience all conditions of the experiment?
It is more likely that participants will work out the aim of the study
What tend to be more of a feature of repeated measures designs than independent groups?
Demand characteristics due to participants being able to work out the aim of the study when experiencing all conditions
What are the strengths of using repeated measures?
Participants variables are controlled, therefore higher validity and fewer participants are needed therefore less time spent recruiting time
What are less of a problem in matched pairs?
Order effects and demand characteristics
What can never happen with participants in matched pairs designs?
Although there is some attempt to reduce participant variables in this design, participants can never be matched exactly
Even when identical twins are used as matched pairs, there will still be important differences between them that may affect the DV
What are the struggles with matching?
Matching may be time-consuming and expensive, particularly if a pre-test is required, so this is less economical than other designs
