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Learner Resource 4IVs, DVs and extraneous variables

All experiments have an independent Variable and a dependent variable:

● The independent variable is manipulated/changed by the researcher, and split into different experimental conditions. You must always operationalise independent variables so others know exactly how it has been manipulated. For example, in a memory test investigating whether students learn better listening to music or not, the independent variable might be one group listening to 1 minute of Taylor swifts “shake it off” played from the beginning whilst learning a word list and the other condition listening to no music at all whilst learning a word list.

● The dependent Variable is the behaviour that is being measured. You must also always operationalise this so other people know exactly how behaviour has been measured. For example, in a memory test investigating whether students learn better listening to music or not, memory could be measured by providing each condition with a list of 20 words to memorise for 1 minute (listening to music or not) and students then have 1 minute to recall the list of words from memory.

Have a go yourselfHow could you operationalise the following variables in this proposed research?

A researcher wants to find out if students learn better in the morning than in the evening

IV =

DV =

A researcher wants to investigate if caffeine affects memory

IV =

DV =

A psychologist wants to investigate if eating cheese before going to bed causes nightmares

IV =

DV=

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Research methods

Extraneous variablesPsychologists want to CONTROL all variables except the one they are manipulating to see if manipulating one variable will result in a change in another variable. Extraneous variables are variables that if not controlled for can confound the results of a study. The researcher needs to control (where possible) any other variable that could interfere with the relationship of the IV and DV. If extraneous variables are not controlled then the validity of the experiment can be questioned and a cause and effect relationship cannot be proven.

TaskUnderneath each of the following experiments identify the IV & DV. Then identify any possible extraneous variables. Finally, suggest how these extraneous variables were or could be controlled/eliminated.

1. In a test to see if music affects our ability to remember, Carrie has put participants into two groups. In group 1 - participants have a list of word pairs to read and listen to Calvin Harris “feel so close to you” whilst learning the words and group 2 participants will simply be asked to read the list of word pairs and do so in silence. Both groups then had 1 min to recall as many of the word pairs from the list as they could.

IV: Possible Extraneous variables?

How they were controlledDV:

2. In an attempt to see just if we get physiologically aroused to soap opera storylines (and hence become addicted!) Conrad set up an experiment. He showed his participants a programme on gardening for half an hour, and then measured their heart rate. Then he showed the same participants a dramatic episode of Hollyoaks, and then measured their heart rate again. They watched the films in the same room.

IV: Possible extraneous variables?

How they were controlledDV:

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Research methods

3. When we become tired our driving is said to suffer. James wanted to test this and gathered 40 participants. 20 of them were only allowed 3 hours sleep on Monday night, while the other 20 were allowed the standard 8 hours. On Tuesday morning at 9am they all sat the Hazard Perception Task used in the driving test. All participants sat the hazard perception task at a driving centre in Manchester city centre. It was expected that less hours sleep leads to more errors!

IV: Possible extraneous variables?

How they were controlledDV:

Version 1 3 © OCR 2017

Research methods

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