Lesson 1 Experimental Methods

Question 1

Independent variable

Answer 1

This is the variable that the researcher manipulates in order to determine its effect on the dependent variable. The independent variable may be divided into levels, sometimes referred to as experimental conditions.

Question 2

Control condition

Answer 2

To provide a standard against which experimental conditions can be compared, there may be a control condition where the IV is not manipulated at all e.g. no chocolate and the effect on mood

Question 3

Dependent variable

Answer 3

This is the variable that is being measured (mood)

Question 4

Extraneous variable

Answer 4

These are any variables other than the IV that COULD affect the DV.

Question 5

Confounding variable

Answer 5

These are any variables (other than the IV) that HAVE affected the DV. Examples include light and noise

Question 6

Operationalisation

Answer 6

For an experiment to be successful, the dependent and independent variables must be operationalised, therefore the variables need to be defined and stated how it will be measured. For example, if measuring aggression in children this must be defined and measured, e.g. ”Aggression means how angry or irritated a person is and this can be measured by displays of verbal or physical acts of aggression in a 10 minute period”

Question 7

Laboratory Experiments

Answer 7

This is when an experiment is carried out in a controlled environment, such as a laboratory, allowing the researcher to exert a high level of control over the IV and eliminate any EV. The researcher can then observe and measure the change in the DV caused by their manipulation of the IV.

Participants (people who take part in psychological research) are randomly allocated to a condition. This means neither the experimenter nor the participants decides which condition the participant is placed in, an unpredictable method (such as flipping a coin) is used to decide.

The other variables than an experimenter wants to hold constant are called extraneous variables. The aim of controlling EVs is to minimize their possible impact on the results of the investigation. An example of extraneous variables may be the participant’s personality or personal experiences

Laboratory experiments are conducted in an artificial setting

Question 8

Advantages of Laboratory Experiments

Answer 8

1. A strength is that laboratory experiments have a very high level of control over the IV and conditions. Therefore it is very easy to control for any extraneous variables and prevent them from becoming confounding variables which might affect the measurements or data collected.
2. A strength is that the researcher can manipulate the independent variable and can establish a cause and effect relationship between the independent variable and the dependent variable.
3. A strength is that a laboratory experiment can be easily replicated (conducted again) by other researchers to see if similar results can be obtained. If the findings are similar to the original study than the results are reliable

Question 9

Disadvantages of Laboratory Experiments

Answer 9

1. A disadvantage of laboratory experiments is that demand characteristics might occur within the study. This is where the participants in the study might guess what the aim of the study is and therefore change their behaviour accordingly which means the data becomes invalid. Some participants behave in a more positive light than normal and this can be called, social desirability bias
2. A disadvantage of laboratory experiments is that establishing a high level of control over the independent variables and extraneous variables, means that the experimental situation can often lack mundane realism (the extent to which an experiment reflects real life). This means the laboratory study does not have ecological validity (the ability to generalise the findings of a piece of research to real life situations or other places/contexts).

Question 10

Field Experiment

Answer 10

This is an experiment carried out in the real world or in a natural setting rather than in the artificial setting of a laboratory. The independent variable is still manipulated or controlled by the researcher to see the effect on the dependent variable. An example might be to observe people in the street.

Question 11

Advantages of Field Experiment

Answer 11

1. A strength of a field experiment is that there is more mundane realism and ecological validity than in a laboratory, and it reflects real life more than a laboratory experiment.
2. An advantage of a field study is that because the researcher can manipulate the independent variable; a cause and effect relationship between the independent and the dependent variable can be established.
3. An advantage of a field experiment is that there is less chance of demand characteristics as opposed to a laboratory experiment. In a field experiment the participants might not even be aware that they are taking part in research and so they will behave more naturally and more valid data will be collected

Question 12

Disadvantages of Field Experiments

Answer 12

1. A disadvantage is that there is less control over extraneous variables when compared to a laboratory experiment. Therefore the effect on the dependent variable may not be caused by the independent variable but by extraneous variables. This means the research is not valid (it is not measuring what it intends to measure).
2. A disadvantage of field experiments is that there is less control over the sample (this is who is taking part in the experiment). Therefore the sample might not be very representative of the target population.
3. A disadvantage of field experiments is that they might be difficult to repeat which means that they might be unreliable, especially when compared to laboratory experiments.

Question 13

Natural Experiments

Answer 13

For this type of experiment the researcher takes advantage of a naturally occurring independent variable to see its effect on the dependent variable

A natural experiment is a study that measures variables that aren’t directly manipulated (caused) by the experimenter, for example comparing behaviour in a single-sex and mixed school. This then means that the independent variable is naturally occurring. Effectively the experimenter is finding participants who already meet the conditions of the experiment, rather than allocating participants to conditions themselves.

Question 14

Advantages of Natural Experiment

Answer 14

1. An advantage of natural experiments is that there is a high level of mundane realism and ecological validity compared to laboratory experiments.
2. An advantage of natural experiments is that they are very useful when it is impossible or unethical to manipulate the independent variable/sample in a laboratory or field experiment. An example might be that psychologists wish to study a naturally occurring event which would otherwise be unethical to impose on participants e.g. a group of naturally stressed men aged 60-65 who have high stress levels and cholesterol

Question 15

Disadvantages of Natural Experiments

Answer 15

1. A disadvantage of natural experiments is that there is low control over extraneous variables compared to a laboratory experiment
2. A disadvantage of natural experiments is that they are very difficult to repeat. This means that they often are very unreliable and if the experiment was repeated, it is very unlikely that the same results would be gained again.
3. A problem of natural experiments is that they are difficult to determine cause and effect due to low levels of control.

Question 16

Quasi Experiments

Answer 16

Quasi-experiments contain a naturally occurring independent variable. However, in a quasi-experiment the naturally occurring independent variable is a difference between people that already exists (i.e. gender, age). The researcher examines the effect of this variable on the dependent variable (DV).

An example might be that males have higher levels of testosterone than females in a sample of 50 men and 50 women aged 40-70. The psychologists might want to study this natural difference between the two genders and see what effect it might have on the dependent variable (aggression levels)

Quasi experiments usually take place in a laboratory setting.

Question 17

Advantages of Quasi Experiments

Answer 17

1. A strength is that there is high level of control. The effects of extraneous variables are minimized, so the experimenter can be more confident that is the independent variable which has affected the dependent variable.
2. A strength is that replication is very likely. Due to strict controls this means it is easier to replicate the study to test reliability of findings.

Question 18

Disadvantages of Quasi Experiments

Answer 18

1. Lack of ecological validity because the setting is artificial experiments may not be a reflection of real-life behaviour.
2. Demand characteristics might be a problem. The participants may either accurately or inaccurately guess the aim of the experiment and respond according to what they think is being is investigated. This can affect the data collected and the results of the study (invalid).