Controls

Specification

• Extraneous variables and confounding variables.

• The use of control groups, counterbalancing, randomisation and order effects.

• Experimenter effects, demand characteristics and control issues.

Extraneous Variables

Extraneous variables are unwanted factors in a study that, if not accounted for, could negatively affect (i.e. confound) the data subsequently collected.

Such factors potentially prevent researchers from finding a direct causal effect between the manipulated independent variables (IVs) and measured dependent variables (DVs) set out in an investigation.

For researchers to be confident that change in the IV will solely affect change in the DV, potential confounds need to be identified and controlled/eliminated; poor control will lead to results with lower reliability.

There are three key considerations to take when controlling extraneous variables:

Participant variables – minimising differences between participants (e.g. their stage of development such as age, or ability such as IQ).

Experimenter variables – factors such as researcher behaviour, appearance or gender could affect participant responses, so should be made consistent throughout the experiment.

Situational variables – control of the setting where the experiment takes place, such as keeping light, sound and temperature levels consistent.

Research Controls

There are several ways in which research can be controlled to eliminate extraneous variables.

Random allocation of participants is an extremely important process in research. In order to assess the effect of one variable on another, all variables other than the variable to be investigated need to be controlled. Random allocation greatly decreases systematic error, so individual differences in responses or ability are far less likely to consistently affect results.

Counterbalancing is a method used to deal with extraneous effects caused by order effects that arise when using a repeated measures design. The sample is split in half with one half completing the two conditions in one order and the other half completing the conditions in the reverse order. Eg, the first 10 participants would complete condition A followed by condition B but the remaining 10 participants would complete condition B then A. Any order effects should be balanced out by the opposing half of participants.

Randomisation is used in the presentation of trials to avoid any systematic errors that the order of the trials might present.

Standardisation refers to the process in which procedures used in research are kept the same. Great attention is taken to keep all elements of a procedure identical, so that methods are sensitive to any change in performance. Under these circumstances changes in data can be attributed to the I.V. In addition, it is far more likely that results will be replicated on subsequent occasions when research is standardised, which means that data reflects a meaningful pattern and was not a one-off chance result.

Demand characteristics are features of the environment that give away the aim of the experiment and, and as a result, changes the behaviour of the participant. This distorts results, as a participant might intentionally try to demonstrate what the researcher is investigating, or display the opposite (the screw you effect). Participants sometimes try to present themselves in a positive light rather than producing genuine responses/ behaviours, this is known as social desirability bias.

Experimenter Effects occur when the presence of the investigator themselves affects the outcome of the research. Eg. during an interview the participants might feel self-conscious or might be influenced by behavioural cues from the researcher (nodding, smiling, frowning etc.).

Past Paper Questions

• Define the term ‘randomisation’. (1) January 2020

2 Markers

• Explain one participant variable that Manon may need to consider when planning her research. (2) January 2018

• Explain how one participant variable could have affected Zulikhat's study. (2) June 2019

• Describe one control that researchers would have considered for the memory game used in this experiment. (2) January 2020

4 Markers

• Explain two controls the researcher may have considered when planning this experiment that tested participant decisions individually and as part of a group. (4) June 2017

• Explain two variables that Philippa may have needed to control when designing her word lists. (4) October 2018

• Explain two improvements Nairi and Talia could make to their memory experiment. (4) January 2019

• Explain, using individual differences, two reasons why the students did, or did not, attend the meeting. (4) January 2020