Lesson 1 Experimental Methods Flashcards
What is an independent variable
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.
An example might be that we want to investigate how chocolate (IV) effects mood.
The experimental conditions might be 10 grams of chocolate, 20 grams of chocolate and NO chocolate
What is a controlled condition
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
What is the dependent variable
This is the variable that is being measured
Hat is an extraneous variable
These are any variables other than the IV that could affect the DV
What is the confounding variable
These are any variables other than IV that have affected the DV
Eg light and noise
What does operationalisation mean
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”
What is a laboratory experiment
When an experiment is carried out in a controlled environment such as a lab allowing the researcher to expert a high level of control over the IV and Eli mate any EV
The researcher can then observe and measure the change in the DV cause 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.
Advantages of a lab experiment
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
Disadvantages of a lab experiment
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).
What is a field experiment
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.
Strengths of field experiments
1) A strength of a field experiment is that there is more mundane realism and ecological validity than in a lab 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
Disadvantages of field experiments
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) 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 replicate which means that they might be unreliable, especially when compared to laboratory experiments.
What is a natural experiment
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.
Advantages of natural experiments
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.
Disadvantages of natural experiment
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 replicate 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.
