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AQA Psychology, Research methods, Experiments

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Helen Isley

on 8 April 2013

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Transcript of AQA Psychology, Research methods, Experiments

Lab Experiments Field Experiments Field experiments take place in a natural setting but the experimenter manipulates the IV. Natural Experiments In a natural experiment, the Independent Variable is not manipulated by the experimenter, it occurs naturally. Experiments Research Methods Experiments When conducting research, psychologists have to choose the best research method to test their theory. They could use: Experiments Observations Questionnaires Interviews Case studies Correlational
Analysis Objective: to understand the use of experiments in psychological research. Outcomes:

to be able to identify and define the different types of experiment.

to be able to explain the elements of the different experiments using psychological terminology.

to be able to evaluate the use of different types of experiment using psychological terminology. An experiment is where you test how a change in one variable (the independent variable) effects the other variable (the dependent variable).

For example, you could test how an increase in alcohol consumption (IV) affects a participants reaction times (DV). The alcohol is the thing which changes in each condition and the reaction time is the thing you are measuring. Can you spot the IV and DV in the following experiments? You conduct an experiment to see if listening to Jedward affects your sanity. In one condition you have a group of people who have not heard Jedward. In the second condition you have a group of people who are made to listen to Jedward for 3 hours.
A psychologist then uses a questionnaire to assess their sanity.
What is the IV? What is the DV? 2. You conduct an experiment to see if noise pollution affects people's stress levels. You visit a sample of people living under the Manchester airport flight path and conduct a stress questionnaire with them. You also visit a sample of people living in a quiet countryside area and conduct a stress questionnaire with them.

What is the IV? What is the DV? You conduct an experiment to see if making eye contact with customers increases the tip they give a waiter. In a local restaurant, half the waiters are instructed to crouch at the table while taking orders, the other half are told to stand upright. They compare tips at the end of a four hour shift.

What is the IV? What is the DV? There are 3 types of experiment:

Lab experiments Field Experiments Natural
experiments Turn to page 3 of your research methods booklet and complete the box at the bottom with a definition of the IV and DV


the IV changes between conditions to see what effect it has on the dependent variable.

the dependent variable is then measured by the researcher. So for example, you want to conduct an experiment on the effects that an increased heart rate has on ratings of physical attraction.

In order to test this, you present 2 groups of participants with a set of photographs which they must rate on a scale of 1-10 for how attractive they are.
One group will do this with a resting heart rate (control condition), one group will do this with am increased heart rate (excercise condition).

What is the IV?
How might you manipulate it?

In order to determine that it is ONLY the heart rate which is having an effect, you need to isolate all the other variables and control them. Read Page 6. A lab experiment takes place in a controlled setting and the researcher manipulates the Independent variable. You should consider:

Participant variables

Situational variables

Experimenter effects

Demand characteristics How could you control these? Apply each of the following evaluation points to a Laboratory experiment: Control over variables- if you are able to control extraneous variables, you know that it is your IV having an effect on the DV and not something else interfering. The more control you have the higher the Internal validity. If you do not control an extraneous variable it becomes a confounding variable which could affect the validity of your results. Replication- if an experiment is easy to replicate, we can re-do to test its reliability (whether we get the same results every time). Demand characteristics: this is where the participants can guess the aim of the study and change their behaviour. Ecological Validity- this is the extent we can generalise the experiment to other settings, the more artificial the setting is, the harder it is to say the same would occur in a real life setting. Bandura used a lab experiment to test whether children learn aggressive behaviour from watching others.

1. What is a lab experiment? (2 marks)

2. Give one strength and one limitation of using a lab experiment to test this. (4 marks) How to answer:

1: State your strength/weakness
2: Explain it
3. Comment on it.

(1) The experiment lacks external validity,
(2) this is because it was a lab experiment, conducted in an artificial setting.
(3) it is therefore difficult to generalise to everyday life. What was the Independent variable in this experiment?

What was the dependent variable?

Why is this different from a lab experiment? How could you evaluate a field experiment? Key Term: Validity Validity means to what extent are your results accurate.

There are two types:

Internal Validity- this looks withIN the experiment to see whether the experimenter measured what they intended to.

External Validity- looks outside the experiment, to how far it can be generalised to different situations. Internal Validity Did the experiment test what the experimenter wanted it to? The experimenter wants to know the effects of the IV on the DV.

If there are confounding variables that could have affected the DV, the experimenter no longer knows what produced the results. Look back to the field experiment we have just seen....

What else could have affected the results?

Is the internal validity HIGH or LOW?

How would you write this? Remember: 1. Make your point
2. Explain it
3. Comment The experiment has low internal validity, this means that you cannot establish whether it was in fact gender (IV) affecting the number of people who helped (DV) because as a field experiment, there is little control of extraneous variables that could have affected the results such as participant variables and situational variables. External Validity This is the extent to which the results can be generalised. There are three types: Ecological Validity This is the extent to which the experiment can be generalised to other settings. The more life-like/natural the setting is, the more you can generalise it to real life settings.

Which type of
experiments would
have the lowest
ecological validity? Population Validity This is the extent to which the experiment can be generalised to different people. For example, if your whole sample was white British, you couldn't say that any other ethnic group would act the same way.

What can you do to improve population validity? Temporal Validity This is the extent to which the research can be generalised to different times. For example, if the Milgram experiment was repeated in modern times, it might show different attitudes towards obedience. What's my validity? Team challenge. Read the article on the St.Helena Island study: Is this an experiment?

Why? / Why not?
(Think about the definition of an experiment) Complete the Experiments Evaluation Table.

If you finish it, complete the definitions of key terms. Feedback A researcher wants to study the effect of noise pollution on people's stress levels. She conducts a stress questionnaire on two conditions on people. The first condition live in a quiet area of countryside. The second condition live under the Manchester airport flight path.

What is the IV? (1 mark)

What is the DV? (1 mark)

What type of experiment is this? Explain. (2 marks)

Give on strength and one limitation of this experiment.
(4 marks.) Peer Mark 1 the level of noise pollution in the area where the participants live. 2 the participants score on the stress test. 3 This is a natural experiment because it takes place in a natural setting and the IV(level of noise pollution) is naturally occurring (not manipulated by the experimenter) 4 For four marks you must have written one strength and explained it well and one weakness and explained it well.


Your points could be:

Low Internal Validity
Lack of control over extraneous variables
Low Reliability

High ecological validity
Low chance of demand characterstics

Lesson 1: Starter 1. Consider the following questions individually.

What is an experiment?
Give an example of an experiment from your study of Psychology so far.
Explain why this is an experiment. 2. Discuss your answer in pairs.
3. Write your final answer on your w/b Exam Style Question:
A psychologist carries out a lab experiment investigating the effectiveness of a strategy for memory improvement. The participants are all selected from the local university. In one condition, participants are taught the strategy, in the other condition they are not.
All participants were asked to memorise 10 pictures of familiar objects. All participants were then given 50 pictures each and asked to select the original 10.

The experiment was criticised for lacking external validity. Explain why. (4 marks) Remember... Make a Point using a key term.

Explain it. (show that you understand the key term)

Comment on it. (relate it to the question/study) Lesson 2 Starter: Team challenge
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