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Research Methods

Lesson 8

Introduction to Quantitative Research Experimental Method Produced by

Laboratory Field Quantitative Natural Research Method


Observations Correlation Surveys Surveysand andInterviews Interviews Case Studies

Key Terms Control Group • This is the group of participants who do not receive the experimental treatment and they act as a control (comparison) to the participants who participate in the experimental condition. Laboratory Experiments • Is an experiment that is carried out in a controlled environment where the independent variable is manipulated.

Field Experiment • An experiment that takes place in a natural environment opposed to a laboratory. The independent variable is still manipulated. • Examples of these environments are schools, hospitals, day care centres and universities. • What you should understand from this approach is that the environment is not simulated in a laboratory.

Natural Experiments • The researcher takes advantage of a naturally occurring difference. • Natural experiments are not true experiments because variations in the independent variable occur naturally opposed to it being manipulated by the researcher. • Natural experiments are sometimes referred to as Quasi experiments. • An example could be an investigation on child development under foster care compared to development with biological parents. Large samples can be obtained an observed in areas affected by the Tsunami disaster.

Ecological Validity • The extent to which the findings from an experiment (i.e. methods, material and settings) can be applied to real life situations.

Introduction • Once the aim and hypotheses has been written, and all the variables to which it refers to are defined and operationalised. • We then try to identify any possible extraneous variables and consider whether our experiment is valid. • Take note : at this point we cannot check for reliability.

• At the back of our mind we have some idea about the possible experimental/participant designs (repeated measure, independent groups or matched pairs) and sampling choices (opportunity, volunteer and random) that are available to us. • We have identified any possible ethical issues (DIP – Deception – Informed Consent and Protection of Participants) and implemented the ethical guidelines.

Aims One tailed Experimental Two tailed

Hypothesis Null

Define All Variables

Variables Operationalised

Including IV

Face Psychometric

Concurrent Predictive

Validity Internal General

Population External Ecological


2 x ADV 2 x Dis ADV 2 x Adv


Volunteer Random

2 x Dis ADV 2 x Adv 2 x Dis Adv


2 x ADV 2 x Dis ADV 2 x Adv

Experimental Design

Independent Matched Pairs

2 x Dis ADV 2 x Adv 2 x Dis Adv

Deception Informed Consent Protection of Participants Withdrawal Ethical Guidelines

Confidentiality Debriefing Observational Research Giving Advice Colleagues

Laboratory Field Quantitative Natural Research Method


Observations Correlation Surveys Surveysand andInterviews Interviews Case Studies



Full Scale

• The next, critical step is to choose an appropriate research method (quantitative – experimental – laboratory – field - natural ) or (qualitative – observations – correlation – surveys and interviews – case studies). • The method chosen must be capable of testing the hypothesis or research question. • Whatever the method selected the researcher must trial it in a pilot study. This should be designed to test the reliability of the data collections tool and the researcher should make any necessary changes before carrying out a full scale investigation.

Quantitative Approach or the Experimental Method • The experimental method is the most powerful and rigorous method used to test a hypothesis and it is the only method that can establish cause and effect relationships. A true experiment has three key features: • Manipulation of an Independent Variable: the independent variable (IV) is directly manipulated by the researcher to produce a change in the dependent variable (DV).

• Randomisation: a true experiment requires that the participants are randomly allocated to the control and experimental condition. • Control: effort is made to control or hold constant all variables other than independent and dependent variable in an experiment. These other variables are known as extraneous or confounding variables. • One way of imposing this control is by having an experimental and control group in your experiment.

Laboratory Experiments Description: • The IV is directly manipulated by the experimenter. • participants are randomly allocated to the control and experimental conditions. • All extraneous or confounding variables are controlled for. • The experiment usually takes place in a laboratory environment.

Advantages: • High levels of control of the independent variable and extraneous variables. • Experiments of this nature can be replicated. • Experiments of this nature can establish cause and effect relationships.

Disadvantages: • Validity - can lack external validity that is both population and ecological validity. • Extraneous variables – high possibility of investigator, participant effects, demand characteristics and situational variables. • Artificiality – the tasks in the experiment can sometimes lack mundane realism

Field Experiments Description: • The researcher controls the independent variable but cannot control extraneous variables to the same extent as in a laboratory. • Participants are not necessarily randomly allocated to the experimental and control conditions.

Advantages: • Cause and effect conclusions can be drawn from this type of experiment. • Often has high levels of ecological validity because the experiment is carried out in a natural environment like a school, day care centre, university or hospital. • Less chance of experiencing demand and participant effects.

Disadvantages: • Less control over extraneous variables. It becomes difficult to control extraneous variables because you are in a natural environment. • Often time consuming. • Random allocation to conditions can be difficult.

Natural Experiment Description: • The researcher does not manipulate the independent variable. • There is no random allocation to the experimental or control condition. • This is a Quasi experiment and not a true experiment.

Advantages: • Useful when it would be unethical or impossible to manipulate the independent variable. • High levels of ecological validity.

Disadvantages: • Problem with internal validity because we cannot control the extraneous variables. • We cannot conclude cause an effect. • No random allocation to condition.

Key Points • The experiment is the most scientific of all research methods. • The experiment allows causal conclusions to be made. • The three criteria for an experiment are: manipulation of the IV, control of the EV’s and random allocation of the participants. • There are three different types of experiment: laboratory, fields and natural.

• Each of the above has advantages and disadvantages that can be judged along the lines of ecological validity, artificiality, control of the IV, control of EVs and ability to make causal conclusions.

Examiners Note • You should be able to offer at least two advantages and disadvantages of the different experiments. • Remember if two marks are available then mere identification of the advantage/disadvantage would only gain you one mark; you need to elaborate to gain the full marks. • For example , stating the disadvantage of the laboratory experiment is that it lacks ecological validity will earn you one mark.

• To gain the second mark you would need to elaborate and write: ‘ It often lacks ecological validity meaning that due to the artificiality of the research situation it may be difficult to generalise the findings to other situations’. • This shows the examiner that you understand what ecological validity means.

Research Methods - Experimental Approach