Chapter 1.1: Experiments Flashcards
Experiment
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
independent variable (IV)
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
dependent variable (DV)
the factor in an experiment that is measured and is expected to change under the influence of the independent variable
uncontrolled variable
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
experimental condition
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)
control condition
a level of the IV in an experiment from which the IV itself is absent. It is compared to one or more experimental conditions.
3 types of experimental design
• independent measures design
• repeated measures design
• matched pairs design.
experimental design
the way in which participants are allocated to levels of the IV
independent measures design
an experimental design in which a different group of participants is used for each level of the IV (condition).
demand characteristics
features of the experimental situation which give away the aims.
random allocation
a way to reduce the effect of confounding variables such as individual differences.
repeated measures design
an experimental design in which each participant performs in every level of the IV
participant variables
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.
confounding variable
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.
demand characteristics
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.
random allocation
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.
repeated measures design
an experimental design in which each participant performs in every level of the IV.
participant variables
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.
confounding variable
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
order effects
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
practice effect
a situation where participants’ performance improves because they experience the experimental task more than once, for example due to familiarity or learning the task
fatigue effect
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.
randomisation
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
counterbalancing
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.
matched pairs design
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.