Psychology Research Methods

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Psychology Research Methods

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The Experimental Method

Psychologists use this method most often. The independent variable is manipulated by the experimenter in order to determine the effect it has on the dependent variable. The dependent variable is the aspect that will be measured. 

    • The experimenter acts on the IV
    • The IV leads to a change in the DV
    • Changes in the DV are measured.

The main way to ensure that changes in the DV are caused by the IV is to keep everything else / all the confounding variables controlled.

Advantages of a Lab Experiment

Disadvantages of a Lab Experiment

Can be easily replicated

It is artificial

Supports theories / provides evidence

It is difficult to control all confounding variables

A cause and effect relationship can be established.

Investigator effects and demand characteristics are involved

It is an original source of knowledge

There are ethical issues

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Psychological theories are tested to see if they are true. As behaviour is so variable, psychologists need to use a wide variety of methods.


    • Quantitative Research – This is when the data measuring behaviour is numerical.
    • Qualitative Research – This method involves extracting from the participants experience i.e. through interviews etc.
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Field Experiments

An  experiment carried out in a ‘natural’ setting (eg a school, train, office etc.) that unlike  the case of laboratory experiments, the setting is not created by the researcher. Field experiments are relatively rare since identifying settings where experimental intervention is both feasible and ethical is difficult. Less artificial than laboratory experiments, fewer variables are controlled, so inferences are often difficult.

An example of this is the study 'Good samaritanism: An underground Phenomon?' by Piliavin et. Al. (1969)

Advantages of a Field Experiment

Disadvantages of a Field Experiment

Behaviour of participants is often more natural. Similar to their normal behaviour

Experimenter may have difficulty controlling every aspect of the situation

Can be replicated

There are ethical issues. As informed consent cannot be obtained as they don’t know they are taking part.

High external validity – can relate results to real life situations.



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Natural Experiments

In natural experiments changes on a variable can be measured but the IV is not manipulated by the experimenter and participants have not been randomly selected / allocated to groups.

Advantages of a Natural Experiment

Disadvantages of a Natural Experiment

Participants behaviour will be more natural

Replication is usually not possible

Data gathered is full and rich

A cause and effect relationship is difficult to establish

Can be used whenever other methods are unethical or impractical

The experimenter does not have total control over the situation.


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Correlation Analysis Method

This method simply looks at the relationship between two variables. However even if a relationship between variables is discovered, it cannot be concluded that one caused the other because there could be other possible explanations. Correlations yield no cause and effect relationship. Correlation coefficient is a mathematical way to shoe how closely related two variables are. The closer the relationship to +1.0 the greater the positive correlation and the closer the relationship to –1.0 the greater the negative correlation.

Advantages of Correlation Analysis

Disadvantages of Correlation Analysis

Allows study of hypotheses that cannot be studied directly

Cannot draw cause and effect conclusions

Can obtain a large amount of data

Interpretation of results can be difficult

Correlation studies can indicate trends which may lead to further experimental research

Ethically – Researchers must be aware that their findings are not misinterpreted and become socially sensitive. (Intelligence and genetics)

Problems of interpretation are reduced when no association is found.


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Naturalistic Observation

This method is designed to examine behaviour without experimenter interference. It is a research method that looks at how people or animals behave in a natural situation. The observer may be disclosed or undisclosed to those taking part. Two types of observation are:

  • Participant observation – the observer actually gets involved and joins in with the group being studied.
  • Non-participant observation – the observer remains external to those being studied.

Advantages of Naturalistic Observation

Disadvantages of Naturalistic Observation

Behaviour will be natural / realistic

The researcher has no control

Useful if other methods aren’t appropriate.

There are problems with reliability and replication

Has high external validity

Some participants might change their behaviour if the know they are being observed

Results are full and rich with information

It can be hard to record information.

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Questionnaire Surveys

The aim is to obtain information of a specific population of interest by administering the questionnaire to a sample of that population. They can be conducted by post, phone, Internet or even in the street. The questions can be closed or open. Closed questions are when the researcher provides possible answers. This is usually used when factual information is required. It makes data easy to analyse but may lack realism due to forced choice of answers. Open-ended questions are when the researcher does not restrict the range of available answers.This provides greater depth of qualitative information but answers are harder to analyse.

Advantages of Questionnaire Survey’s

Disadvantages of Questionnaire Survey’s


Lack of quality

Easy and simple to create and carry out

Distorted data


Easy to write leading questions

Varied sample

Researcher effects – influence from researcher

Can gain qualitative and quantitative information

Ambiguous / unclear questions

Versatile – it can be used in a range of different situations

Closed questions are easy to analyse

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This can be a face-to-face situation where one person (interviewer) asks questions to another (the respondent). There are four different types of interviews; structure, semi structured clinical and unstructured.

Structured Interviews

These contain fixed pre-determined questions and ways of replying ie yes, no, don’t know. E.g. A market research interview.


Advantages of a Structured Interview

Disadvantages of a Structured Interview

There is less chance of deviating from the topic

Less validity- The researcher cannot follow up on new / interesting lines of enquiry

It is easy to analyse


There is less risk of interviewer bias


Interviewees can be compared


Are reliable and replicable


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Semi Structured Interviews and Clinical Interviews

Semi Structured Interviews

This may be the most successful approach as there are some prepared questions and the interviewee can expand their answers.

Advantages of Semi Structured Interviews

Disadvantages of Semi Structured Interviews

Flexible and Reliable

Particular phrasing of questions could lead to low reliability

Sometimes easy to analyse and compare

Very open ended questions / answer’s are difficult to analyse

 Clinical Interviews

These are used to assess peoples mental state., it is structured but open ended.

Advantages of Clinical Interviews

Disadvantages of Clinical Interviews


Flexibility can lead to difficulty in replication


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Unstructured Interviews

These may contain a topic area for discussion but there are no fixed questions or ways to answer. Unstructured Interviews dont have a set format but in which the interviewer may have some key questions formulated in advance. Unstructured interviews allow questions based on the interviewee's responses and procedes like a friendly, non-threatening conversation. However, because each interviewee is asked a different series of questions, this style lacks the reliability and precision of a structured interview.

Advantages of Unstructured Interviews

Disadvantages of Unstructured Interviews

Good validity – Interviewees will say what they think

Not always reliable

Complex issues can be explored

It is difficult to analyse data

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Research Design

When designing an experimental study, the researcher must have an aim and a hypothesis. The aim is a general statement explaining why the study is being conducted. The hypothesis explains what the study is designed to test. It is a proposition made so that it can be tested to see if its true.

  • A Directional / One Tailed Hypothesis – Predicts a particular direction eg Higher.
  • A Non Directional / Two Tailed Hypothesis – States there will be a difference.
  • A Null Hypothesis – States that there will be no effect / change.

 Once the aim and hypothesis has been decided the next step is to identify an appropriate design. To compare two groups with regards to the IV it is vital that the participants in each group do not differ in any significant ways. Therefore the way in which participants are selected for experiments has to be carried out carefully. There are three research designs that are available to use; Independent Groups design, Matched Pairs design, or Repeated Measures design.

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Independent Group Design & Matched Pairs Design

Independent Group Design

Each participant is selected for one group / condition. Participants are selected at random, i.e. names out of a hat, tossing a coin etc.

Advantages of the Independent Group Design

Disadvantages of the Independent Group Design

There are no problems with order effects

There may be significant individual differences to start with.

No participants are lost between trials

More participants are needed than within a repeated measures design

 Matched Pairs Design

 The design uses two separate groups of people matched on a one to one basis on variables such as age, gender etc. this controls some individual differences.

Advantages of the Matched pairs Design

Disadvantages of the matched Pairs Design

It controls some of the individual differences

Can be difficult to accurately match pairs.

More participants are needed than with Repeated measures.

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Repeated Measures Design

This design uses the same participants in both conditions. The advantage of this is there is less concern for individual differences affecting the results because the same participants are being used. But there may be problems with order effects i.e. they may perform better in the second condition as they have had practise or they may perform worse as they are bored or tired.

 This could be counter balanced by having half of the group do condition 1 and the other half do condition 2 and then they swap. Therefore order effects will be balanced out. 

Advantages of the Repeated Measures Design

Disadvantages of the Repeated Measures Design.

Controls all individual differences

Participants are likely to guess the aim / purpose of the study.

Requires fewer participants than the other designs


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Selecting Participants

Random Sampling – This is a sample in which every member of the target population has a chance of being selected. Tossing a coin, picking names out of a hat etc, could do this. BUT it is almost impossible to have a truly random sample, as a total list of the target population cannot truly be identified.


Systematic Sampling  - This is a modified version of random sampling that may involve selecting every 10th person from a phone book or selecting every 5th house in a street. BUT there may be participants that refuse to take part.


Opportunity Sampling – This involves using who ever is available and willing to take part. BUT this is not a representative sample and is usually bias, i.e. all one gender, friend’s / colleagues of the researcher. 

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Important Factors Associated with Research Design

In order for research to be properly conducted there are certain guidelines that should be followed. These are:

  • Standardised instructions – Every participant must be given the same instructions.
  • Standardised Procedures – All participants should be treated the same way, e.g. given the same amount of time to complete the task etc.
  • Control of Variables – as far as possible confounding variables must be controlled.
  • Operationalisation – How the DV is being measured, it needs to be clearly defined i.e. to measure performance in Short Term memory we could look at the number of words recalled.
  • Pilot Study – This is a small scale study carried out before the main one to check procedures, design etc. it will also highlight any problems so adjustments can be made before the real experiment. 
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Relationships between Researchers and Participants

With the experimental method there is interaction between the researcher and the participants, which could pose problems to the study. Such as Participant Reactivity – This refers to a situation in which knowing that you are being studied affects behaviour. Regardless of the IV behaviour may change because they are being analysed.

One example of this is demand characteristics. This is when:

·        Participants do their best to be good and try to guess what’s expected of them.

·        Participants try to do the opposite of what’s expected.

·        Participants may look out for ‘tricks’ so they can avoid being caught.

A double blind technique can be used to reduce demand characteristics, which is when participants do not know what condition they are in. they are given a false account of the experiment to prevent them seeking clues. 

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Investigator Effects

 Investigator effects are when the researcher(s) unintentionally affect the results due to the procedures of the research itself. For example, when the subjects of research act differently due to the actions of the people conducting the research. This would create invalid research results.

The researcher can also affect the results of their experiment. Their expectations, personal attributes etc can have an effect on participant’s behaviour. One effect is called experimenter expectancy in which the experiments expectations have an effect on the participant’s performance. 

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Ethical Issues in Psychological Research

  • Informed Consent – Before deciding to take part in research participants should be told the details of the study so they can make an informed decision. Parental consent is needed before studying anyone under the age of 16.
  • Deception – Participants should not be deceived. However if deception is used then participants must be debriefed afterwards. I.e. the real purpose of the study is explained.
  • Protection of Participants from Mental or Physical Harm – Participants should not suffer psychological harm during the study.
  • Right to Withdraw – Participants should be aware that they could leave during the study or withdraw their data at the end.
  • Privacy – Data collected should be treated confidentially.
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Internal and External Validity

Internal Validity

This refers to whether the results are valid and can be linked to the manipulation of the IV. Results are internally valid if they have not been affected by confounding variables. Also there should be;

  • No investigator effects
  • No demand characteristics
  • Use of standardised instructions
  • Use of a random sample

 External Validity

This refers to whether the results can be generalised beyond the experimental setting. Can the results be generalised to;

  • Wider populations (i.e. women)
  • Locations (i.e. outside the lab)
  • Current climate / time
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Reliability & Measures of Dispersion


This refers to the extent to which the results are consistent. E.g. a persons IQ should be similar if not the same when tested again.

How Can we Ensure Reliability?

The test-re-test method is when the same test is given to the participants on another occasion to check that scores are similar.

Measures of Dispersion

This indicates the extent to which scores cluster around the mid point. The way to measure it is working out the range. Which is the highest score take away the lowest which is simply the difference between the two.

Advantage of the Range

Disadvantage of the Range

It is easy to calculate and takes into account extreme scores

Can be influenced by one score that is very different from all the others.

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Descriptive Statistics

Once an experiment is completed there is a set of raw data. Two things can be done with this data, there are measures of Central Tendency and Measures of Dispersion.

Measures of Central Tendency: The Mean, Median and Mode.

The Mean is when all the results are added up and divided by how many there are.

Advantage of the Mean

Disadvantage of the Mean

It takes all scores into account

It can be misleading if there are extreme scores.

The Median is the middle score when the data is arranged in order.

Advantage of the Median

Disadvantage of the Median

It is unaffected by a few extreme scores

It ignores most of the scores

The Mode is the most common score

Advantage of the Mode

Disadvantage of the Mode

It is unaffected by one or two extreme scores

Less sensitive

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brilliant !


unstructured interviews, it says good validity-interviewees will say what they think., but i think face to face there would be demand characteristics, which lower the internal validity


It was helpful but the bottom half of it has been cut off and I can't seem to scroll down to read the rest? Is it happening just to me or is it like that?


Thanks Matt, this is really useful!

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