Research Methods Booklet 1: Key Definitons

Experiment

Involves an IV and DV, which creates groups (conditions) where a difference is investigated

Independent Variable. (IV)

The manipulated variable. (Creates the groups)

Dependent variable. (DV)

The measured variable. (Usually performance / measured numerically.)

Operationalisation.

The precise measurement of variables so they are clearly defined.

IV means referring to both conditions.

For the DV, this means saying exactly how this was measured, referring to a numerical value.

Experimental Condition.

The conditon that receives the IV.

Control Condition.

The conditon that doesn’t receive the IV. (acts as a baseline measurement - a comparison.)

Aim.

An aim is a clear and precise statement of the purpose of the study.

Hypothesis.

A hypothesis is a testable statement that predicts what the researcher thinks will happen in the study. (always in the future tense.)

Directional / one tailed.

Say that the IV will have an effect but do not say what the effect is.

Non-Directional / Two Tailed

Say that the IV will have an effect but do not say what effect is

Experimental Hypothesis.

Used in experimntal methods - says the IV will affect the DV (a difference.)

Null Hypothesis.

Says there will be no difference between the IV or DV.

Extraneous Variable.

Any variable other than the IV that has an unwanted effect on the DV.

Participant Variable.

Differences between participants that might affect performance.

Situational Variable.

Aspects of the setting or materials used (or any environmental variable.) that could have affected performance.

Participant Reactivity.

Changes in the behaviour of the participants due to knowing they are being studied. (these include demand characteristics and social desirability.)

Demand Characteristics.

Where the participants guess the aim of the research and change their behaviour because of this.

Social desirability Bias.

Where participants feel the need to show themselves more positively infront of others.

Investigator effects.

When the investigator inadvertantly influences the participants behaviour, for example, with their instructions, facial expressions, body language etc.

Standardisation.

Variables are kept constant for all participants in all conditions to control for situational variables.

Singled blind technique.

Where the participants are unaware of the condition they are in e.g. drug vs. placebo.

Reduces demand characteristics.

Deception.

Where the participants are lead to believe the research is about something different than it actually is or are withheld the aim.

Reduces participant reactivity.

Standardised instructions.

Exactly the same instructions should be read in the exact same way to each participant. Often done in the form of a script.

Reduces investigator effects.

3rd party researchers.

A third-party researcher is often requested to interact with the participators in place of the lead investigator as they are unaware of the aim and cannot convey the aim inadvertantly.

Reduces investigator effects.

What is random allocation?

The use of chance to place study participants into different groups, such as an experimental or control group.

Reduces researcher bias.

How is random allocation done?

1. Assign each participant a number.

2. Write the numbers of slips of paper, fold, and place into a hat.

3. The first number drawn goes into condition A, then the next goes into condition B. Repeat until all participants have bee assigned a condition

Experimental design

This refers to how we will allocate our participants to the conditions of our independent variable.

Independent Groups Design

This is where two groups of participants experience a different condition of the IV. The participants only experience one conditon

Repeated Measures design

All participants experience both conditions of the IV. Depending on the IV, it is sometimes done as a before + after design e.g. before and after the manipulation of the IV.

Order Effects

Repeating two tasks may cause boredom or fatigue which could make performance worse on the second task. Alternatively, practice effects could improve the performance on the second task.

Counterbalancing

A way to reduce order effects in a repeated measures design. This is done by balancing out problems such as fatigue and practice so that they don’t just occur in the second condition

How to Counterbalance

Instead of:

20 ppts - A → B

Do:

10 ppts - A → B

10 ppts - B → A

*This doesn’t remove order effects, it just balances them out so they occur in both conditions.

Matched Pairs Design

Participants are pre-tested on a variable which is important to control the participants. They are matched into pairs based on that key variable. One participant will go into condition A whilst the other goes to condition B.

Validity

Internal Validity

The extent to which you are measuring what you intend to. (How controlled your study is)

External Validity

Ecological Validity

The extent to which a studies findings generalise to other settings / real life

Population Validity

Temporal Validity

Mundane Realism

Laboratory Experiment

Carried out in a controlled setting. Involving direct manipulation of the IV

Field Experiment

Carried out in a natural setting, involving direct manipulation of the IV

Natural Experiment

(External)

Conducted in a natural environment like the Field Experiment, however, there is no direct manipulation of the IV - the IV occurs naturally and the researcher comes along afterwards to study this.

Quasi Experiment

(Internal)

Can be conducted in a natural or controlled setting. (More often controlled.) The IV is not manipulated by the researcher because it is based upon existing differences between people. e.g. Gender, Age, Phobia vs. Non-Phobia etc.