Psychology: Basics
· Idependent group- Different groups of people participating in the control and experimental. Participants only experience one condition of the IV.
· If for example you were testing how age affects memory recall you may have different groups of people of specific age ranges from one group to another. One group may have teenagers aged 12-19 while another group may have adults aged 25-35. Participants may be randomly selected based purely on age to insure fair allocation between the groups. The IV here may be the different age ranges with each group tested using the exact same conditions.
Strengths – Advantages
Participants can be randomly allocated to try address individual differences that may affect results.
Another strength is there are no “order effects” with the participants being exposed to the experimental condition only once unlike a repeated measures design where participants experience each condition one after another. Participants are also unlikely to be bored or tired in this design which may affect their results as they work through the different experimental conditions.
More participants tend to be used overall compared to repeated measures meaning the results may have more external validity to wider generalisation.
Independent group designs only need participants to complete the conditions once and if the different conditions are run at the same time this can result in a much quicker experiment than a repeated measures design which may be more time consuming.
Weaknesses – Disadvantages
The study requires more participants which may mean the study takes longer to gather them compared to a repeated measures design where you can re-use a smaller sample.
There may still be important significant individual differences between participants that may not be randomly filtered out through allocation resulting in skewed results. This may reduce internal validity and reliability of results.
Repeated Measure Design
· The same group of people participate in both the control and experimental conditions. Participants experience both the conditions of the IV. Group will split, and experience control/experimental, and then switch this is called counterbalancing.
Example:
You wish to test whether pictures and words help in recall vs only words alone. You have a group of 20 participants and test them in the first condition which is pictures and words and then you use the same group members to test them in the second condition which is words alone (different set of words but of similar difficulty/syllables etc). You then check the results.
Strengths – Advantages
· One major strength is you require less group members as you simply re-use the same participants. This means the experiment is done much quicker than gathering participants between conditions like in an independent group design experiment.
· Another advantage is there is no risk of individual differences affecting the results between the different conditions as participants are effectively comparing against themselves.
Weaknesses – Disadvantages
· “Order effects” may occur where participants become better in the second condition due to practice from the first leading to improve or biased results.
· Participants may also display “demand characteristics” if the experiment results in them guessing what the purpose of the study is. The design can not be used where they may “learn” from the first condition which may affect the results in the second.
· Participants may become bored or tired between the two conditions possibly affecting the results in the second condition.
Matched group design
· Participants in control group and exp group are different, however they are matched on one or more characteristics. Eg. A 25 year old male participant in a control group may be matched with a 25 year old male in the experimental group. This is to eliminate a specific variable, in this case age and gender, from affecting the DV.
Example:
You have two groups both being tested on memory recall. Both groups have participants that have been matched as closely to one another as possible based on relevant traits such as age, gender, similar background etc. The IV may be different methods of testing recall such as words only or words and pictures. The two groups would be tested with one group doing words only while the other group does pictures and words. As each participant is believed to be accordingly “matched” they compare the results to see which condition (words only or words and pictures) results in better recall.
Strengths – Advantages
· Matching participants as close as possible on measurable traits may help control for individual differences affecting the results.
· This design is better suited when a repeated measures design may not work due to an order effect occurring which may affect results.
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Weaknesses – Disadvantages
· Trying to match participants for similar traits is very time consuming.
· Trying to match people exactly is impossible as there will always be individual differences from one person to another. Therefore the study may lack internal validity if these differences affect the IV rather than the experimental condition.
· The sample may be smaller as trying to find a large sample of people matching across similar traits may be difficult. This may mean the findings may lack external validity.
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4. Identify features of an experiment
5. Identify DV, IV, EV and CV's
dv- the dependent variable is the unhanged variable of an experiment unaffected by the iV
iv- the independent variable is the variabke that is being tested eg; the type of tv show a child watches and how much they sleep. The dv would be the amount of sleep
ev- the extraneous variable is a variable that may have an effect
A simple example: you want to know if online learning increases student understanding of statistics. One group uses an online knowledge base to study, the other group uses a traditional text. Extraneous variables could include prior knowledge of statistics; you would have to make sure that group A roughly matched group B with prior knowledge before starting the study. Other extraneous variables could include amount of support in the home, socio-economic income, or temperature of the testing room.
cv- Confounding variables are factors other than the independent variable that may cause a result. In your caffeine study, for example, it is possible that the students who received caffeine also had more sleep than the control group. Or, the experimental group may have spent more time overall preparing for the exam. Those factors - sleep and extra preparation - could also create a result that has nothing to do with the caffeine. You cannot be sure that the caffeine caused your result instead of the confounding variables. One way to avoid this type of confound is to randomly assign people to the study.
6. Discuss reliability and validity b
- reliability = consistent measuring of responses each time a research investigation is repeated, only achieved if the research is conducted the same each time
. if the sam procedure is applied and the same results are found than th eeperiment is deemed reliable
. two forms- internal= across items within a test, external= between tests
-Validity =Investigation Into whether the test measures what it claims to measure
7. Identify "samples" and "populations"
Sample: participants being studied in an experiment. Subsection or small group of research participants selected from a large group (participants).
Population: a population refers to the entire group of research of which a sample is drawn.
Key terms and definitions
Independent Groups designs- different groups of people participating in the control and experimental conditions. Participants only experience one condition of the independent variable.
Control group is never exposed to the independent variable.
Repeated Measures design- the same group of people participate in both the control and experimental conditions. Participants experience both the conditions of the IV. Counterbalancing is needed to avoid order effects.
Counterbalancing: a technique that is used when you are using a repeated measures design.
Matched Groups design- participants in control groups and experimental groups are different, however they are matched on one or characteristics. For example: Age more or Gender. A 25 year old male in the control group must be matched with a 25 year old male in the experimental group.
Participant Variable: what is referred to as the egg shell rule. You cannot account for everybody's nuance. Which mean that every one is different emotional and different in their own way.
Order effects: what happens to your data set if your participants anticipate what is going to happen next so there is bias. This often happens when a psychologist forgets to counterbalance.
Population: a population refers to the entire group of research of which a sample is drawn.
Sample: participants being studied in an experiment. Subsection or small group of research participants selected from a large group (participants).
Random Sampling: randomly allocating people into a group. It can be selected via a lottery procedure (name drawn out of a hat).
Stratified sampling: involves dividing the population into different subgroups (or strata), then selecting a separate sample from each subgroup,
Convenience sampling: This is grabbing people who are available or volunteer to be a part. This maybe easy but you know nothing about your subjects.
Random Allocation: Way in which the participants are assigned to either the experimental group or control group. Participants selected are just as likely to be in experimental group as the control group.
Single Blind- participant does not know what group they are in.
Double Blind- the experimenter and participants do not know what group they are in
Placebo Effect: the participants behaviour being influenced by their expectations of how they should behave, caused by the belief that they have received some treatments
