Chapter 1.1: Experiments

Question 1

Experiment

Answer 1

An investigation that allows researchers to look for a causal relationship; an independent variable is manipulated and is expected to be responsible for changes in the dependent variable

Question 2

independent variable (IV)

Answer 2

the factor under investigation in an experiment that is manipulated to create two or more conditions (levels) and is expected to be responsible for changes in the dependent variable

Question 3

dependent variable (DV)

Answer 3

the factor in an experiment that is measured and is expected to change under the influence of the independent variable

Question 4

uncontrolled variable

Answer 4

a variable that either acts randomly, affecting the DV in all levels of the IV, or systematically, i.e. on one level of the IV (called a confounding variable) so can obscure the effect of the IV, making the results difficult to interpret, the effects of which have not or cannot be limited or eliminated

Question 5

experimental condition

Answer 5

one or more of the situations in an experiment that represent different levels of the IV and are compared (or compared to a control condition)

Question 6

control condition

Answer 6

a level of the IV in an experiment from which the IV itself is absent. It is compared to one or more experimental conditions.

Question 7

3 types of experimental design

Answer 7

• independent measures design
• repeated measures design
• matched pairs design.

Question 8

experimental design

Answer 8

the way in which participants are allocated to levels of the IV

Question 9

independent measures design

Answer 9

an experimental design in which a different group of participants is used for each level of the IV (condition).

Question 10

demand characteristics

Answer 10

features of the experimental situation which give away the aims.

Question 11

random allocation

Answer 11

a way to reduce the effect of confounding variables such as individual differences.

Question 12

repeated measures design

Answer 12

an experimental design in which each participant performs in every level of the IV

Question 13

participant variables

Answer 13

individual differences between participants (such as age, personality and intelligence) that could affect their behaviour in a study that would hide or exaggerate differences between levels of the IV.

Question 14

confounding variable

Answer 14

an uncontrolled variable that acts systematically on one level of the IV so could hide or exaggerate differences between levels and therefore ‘confound’ or confuse the results making it difficult to understand the effect of the IV on the DV.

Question 15

demand characteristics

Answer 15

features of the experimental situation which give away the aims.
They can cause participants to try to change their behaviour, for example to match their beliefs about what is supposed to happen, which reduces the validity of the study.

Question 16

random allocation

Answer 16

a way to reduce the effect of confounding variables such as individual differences. Participants are put in each level of the IV such that each person has an equal chance of being in any condition.

Question 17

repeated measures design

Answer 17

an experimental design in which each participant performs in every level of the IV.

Question 18

participant variables

Answer 18

individual differences between participants (such as age, personality and intelligence) that could affect their behaviour in a study that would hide or exaggerate differences between levels of the IV.

Question 19

confounding variable

Answer 19

an uncontrolled variable that acts systematically on one level of the IV so could hide or exaggerate differences between levels and therefore ‘confound’ or confuse the results making it difficult to understand the effect of the IV on the DV

Question 20

order effects

Answer 20

practice and fatigue effects are the consequences of participating in a study more than once, for example in a repeated measures design. They cause changes in performance between conditions that are not due to the IV, so can obscure the effect on the DV

Question 21

practice effect

Answer 21

a situation where participants’ performance improves because they experience the experimental task more than once, for example due to familiarity or learning the task

Question 22

fatigue effect

Answer 22

a situation where participants’ performance declines because they experience the experimental task more than once, e.g. due to physical tiredness or boredom with the task.

Question 23

randomisation

Answer 23

a way to overcome order effects in a repeated measures design. Each participant allocated to perform in the different levels of the in a way that ensures they have an equal chance o participating in the different levels in any order

Question 24

counterbalancing

Answer 24

a way to overcome order effec in a repeated measures design. Each possible orde of levels of the IN is performed by a different sub. group of participants. This can be described as an ABBA design, as half the participants do conditio
A then B, and half do B then A.

Question 25

matched pairs design

Answer 25

an experimental design in which participants are arranged into pairs.
Each pair is similar in ways that are important to the study and one member of each pair performs in a different level of the IV.