experiments types and design

A lab experiment is a type of research method in which the researcher can exert high levels of control over what happens as part of the experimental process.

Lab experiments use a standardised procedure to ensure reliability.

True. It is easier to establish a cause-effect relationship between the independent variable and the dependent variable than for other methods used in psychology. This is due to the use of controls and the objective nature of the research.

b. The use of artificial tasks means that lab experiments lack ecological validity.

A field experiment is a research method which takes place in a natural setting, away from the lab.

False. Field experiments do involve a researcher-implemented independent variable.

a. Field experiments reduce the degree of artificiality experienced by the participants, which gives them good external validity.

It is difficult to replicate field experiments, which in turn reduces the ability to check for reliability.

A natural experiment consists of research into naturally occurring phenomena. The independent variable is not manipulated by the researcher as it is pre-existing, e.g., comparing the difference in development between English and Romanian adoptees.

c. The experience of recalling a list of digits whilst loud music is playing is not an example of a natural experiment.

Natural experiments allow the researcher to investigate topics that would otherwise be unethical to study using a traditional lab experiment.

b. Natural experiments lack reliability because the researcher cannot be sure as to what effect the phenomenon has had on the participants - they have to rely on the accounts of the participants.

A quasi experiment consists of research into naturally occurring phenomena where random allocation to conditions is not possible. The independent variable is not manipulated by the researcher, as it is a pre-existing characteristic of the individual, e.g., comparing the difference in reading ability between children with blue eyes and brown eyes.

d. The performance of people who memorise words with music playing versus people who memorise words with no music playing is not a quasi experiment.

False. Quasi experiments can be run in the same way as a 'true' lab experiment. The independent variable is not manipulated by the researcher as it would be in a 'true' lab experiment.

b. Due to the quasi experiment's lack of manipulation of the independent variable the results could be said to be higher in external validity.

As participants cannot be randomly allocated to condition in a quasi experiment this can lead to participant variables, making it difficult to determine causality.

An independent groups design is where participants only experience one condition of the independent variable.

c. Independent groups design generates unrelated data Unrelated refers to the fact that two separate groups are used so that each group generates its own data set.

Random allocation to condition is done to avoid researcher bias.  

A strength of independent groups design is that demand characteristics are unlikely to act as a confounding variable.

True. A limitation of independent groups design is that participant variables may affect the validity of the findings. This can happen if more participants with a particular characteristic (e.g., a good memory) are all randomly allocated to one condition.

A repeated measures design is where participants experience all conditions of the independent variable (e.g., the experimental condition and the control condition).

a. Repeated measures design generates related data. Related refers to the fact that each participant's score for condition 1 is compared to their score for condition 2.

a. A limitation of a repeated measures design is order effects, which consist of fatigue, practice, and boredom.

Counterbalancing is implemented by having half of the participants experience condition 1 followed by condition 2 and vice versa for the other half of the participants.

A matched pairs design is one in which participants are matched based on a specific characteristic or variable that is important for the research they are taking part in.

a. As each participant is related* to* their counterpart per pair, this design generates related data.

Matched pairs design controls for individual differences as a confounding variable, which is a strength as it increases reliability.

True. Matching is a difficult and time-consuming process It is often impossible to match the participants across all of the criteria, especially when the unmatched characteristic could be important to the results of the research.

c. If one participant drops out of a matched pairs study then the researcher has to find someone very similar to replace them which has economic implications because funding could be removed.