Variables and controlling them

What is an Independent Variable?

What the researcher changes or manipulates to see how it affects something else, it’s the cause in the cause-and-effect relationship.

What is a Dependent Variable?

This is what the researcher measures — the outcome or effect, It depends on the independent variable.

What are the levels of the IV?

The different conditions or versions of the independent variable that are compared in a study.

• E.g. Control condition vs. experimental condition

What is operationalisation of variables?

Clearly defining variables in terms of how they will be manipulated (IV) or measured (DV) in a study.

• It’s done so the variables are clear, measured and replicable to other researchers

How do you operationalise the IV?

The researcher needs to set up and define each condition so that it’s clear that a difference between the conditions is investigated.

• E.g. Participants in condition 1 drink 200ml of a caffeinated drink prior to a memory test; participants in condition 2 drink 200ml of water before a memory test (clear wording)

How do you operationalise the DV?

The researcher needs to design a procedure which enables relevant and appropriate data to be recorded/collected per participant with no ambiguity involved.

• E.g. The number of correctly recalled items from a list of 15 words (identifies how participant performance is to be measured (number of correctly recalled items))

What is randomisation?

The use of chance methods to reduce researcher/investigator bias and control for extraneous variables when designing or running an experiment to keep the research as objective as possible.

• A form of control that researchers use, as it excludes the possibility of bias invalidating the research

• Can be done by selecting names one by one out of a hat or by using random name-generator software

Give an example of randomisation in a memory experiment.

Randomly generating the order of words in a list or the order of experimental conditions for each participant.

• So the position of each word isn’t decided by the participant

What is standardisation?

Identical procedures (same environment, information etc.) set up in a study across all conditions/participants. This is done so no participant receives an unfair advantage or is treated any differently than any of the other participants.

• Having standardised instructions mean that non-standardised changes (the different conditions) in a procedure don’t act as extraneous variables

What is counterbalancing?

This is when half of the participants do conditions in one order and the other half do it in the opposite order. To average/balance out order effects.

• Often used when carrying out a repeated measures design to control for potentially confounding variables

What is the control condition?

The condition where the IV is not applied or is kept at a baseline, used for comparison.

What is the experimental condition?

The condition where the IV is manipulated to test its effect on the DV.

What are extraneous variables?

Any unwanted variables other than the IV that could affect the DV if they’re not controlled.

• E.g. time of day, BG noise, difficulty

Why must extraneous variables be controlled?

Because they can interfere with the results, reducing the study’s internal validity.

What are situational variables?

Features of a research situation that may influence participants behaviour.

• E.g. order effects, time of day, temperature, noise, instructions given or lighting

What are participant variables?

Any characteristics of the individual participants. This is related to individual characteristics of each participant that may impact how they respond.

• E.g. background, mood, anxiety, intelligence awareness or other characteristics that are unique to each person

What are investigator effects?

Any (unintentional) influence of the researcher’s behaviour/characteristics on participants/data/outcomes - these cues may be unconscious nonverbal cues.

• E.g. muscular tension or gestures or vocal cues like the tone of voice

What are order effects?

Can occur in a repeated measures design, and refers to how the positioning of tasks influence the outcome.

• E.g. practice effect (the performance in the 2nd condition may be better because the participants knows what to do) or fatigue effect (worse performance in the 2nd condition because they’re tired) or boredom effect

What are demand characteristics?

When the participants try to make sense of the research by picking up on any cue from the research situation that may be interpreted by the participants as ‘revealing the purpose of the investigation’.

• This may lead to the participants changing their behaviour by acting in a way that they believe are the aims of the investigation (what the researcher is trying to find)

What are nuisance variables?

Any variable other than the IV that could affect the DV and needs to be controlled to prevent it becoming a confounding variable.

• E.g. An experiment testing if caffeine improves memory. Time of day, people generally remember things better (e.g. morning vs evening). It’s a nuisance variable because time of day could affect memory, it can be controlled by testing all participants at 10am

What are confounding variables?

A variable other than the IV which has an effect on the DV. They vary systematically with the IV, which makes it difficult for the researcher to be sure of the origin of the impact of the DV as the confounding variable (not the IV) could’ve been the cause.

• E.g. A experiment testing the effects of caffeine on memory. If some participants slept 2 hours and others slept 8 hours, memory could be affected by sleep, not caffeine. So you can’t be sure caffeine caused the change — sleep is confounding the results

What is the difference between a nuisance variable and confounding variable?

A nuisance variable could affect the DV but the research controls it, so it doesn’t affect the results whereas a confounding variable does affect the DV because the researcher failed to control it.

• Nuisance variable = controlled

• Confounding variable = not controlled