Chapter 1: Research methods
1.1 Experiments
Experiment: an investigation looking for a casual relationship in which an independent
variable is manipulated and is expected to be responsible for changes in the dependent
variable.
Independent variable: the factor under investigation in an experiment that is
manipulated to create two or more conditions, and is expected to be responsible for
changes in the dependent variable.
Dependent variable: the factor in an experiment that is measured and is expected to
change under the influence of the independent variable.
Extraneous variable: any variables that you are not intentionally studying in the study,
yet could affect the dependent variables of the experiment.
Experimental condition: one or more of the situations in an experiment that represent
different levels of the IV and are compared
Control condition: a condition that does not involve exposure to the IV, and is
compared to other experimental conditions. People assigned to the control group serve
as the basis of comparison for the people in the experimental condition
Experimental design: the way participants are allocated to levels of the IV
● Independent measures design: a different group of participants is used for
each level of the condition
● Repeated measures design: each participant performs in every level of the IV
● Matched pairs design: participants are arranged into pairs. Each pair is similar
in ways that are important to the study, and one member of each pair performs at
a different level of the IV.
, ADV: Independent measures DISADV:
● Different participants are used ● Participant variables can affect results
in each level of the IV so there if there are important individual
are no order effects differences between participants in
● Participants see only 1 level of different levels of the IV
the IV, reducing the effect of ● More participants are needed than
demand characteristics repeated measures
● Random allocation to levels of ○ May be hard to find
the IV can reduce the effects of ○ Less effective if there is a small
individual differences sample
ADV: Repeated measures DISADV:
● Participant variables are unlikely to affect ● Order effect could affect
the result as each participant does all result
levels ○ Counterbalancing
● Counterbalancing reduces order effects ● Greater exposure to demand
● Uses fewer participants than characteristics
independent measures so is good when ○ See the experimental
participants are hard to find task more than once
ADV: Matched pairs DISADV:
● Participants see only 1 level of the ● The similarity between pairs is
IV, reducing the effect of demand limited by the matching process
characteristic ○ Right matching criteria
● Participant variables are less likely must be chosen in advance
to affect the result than in to be effective
independent measures as ● Availability of matching pairs may
individual differences are matched be limited
● No order effects ○ Making the sample size
small
1.1 Experiments
Experiment: an investigation looking for a casual relationship in which an independent
variable is manipulated and is expected to be responsible for changes in the dependent
variable.
Independent variable: the factor under investigation in an experiment that is
manipulated to create two or more conditions, and is expected to be responsible for
changes in the dependent variable.
Dependent variable: the factor in an experiment that is measured and is expected to
change under the influence of the independent variable.
Extraneous variable: any variables that you are not intentionally studying in the study,
yet could affect the dependent variables of the experiment.
Experimental condition: one or more of the situations in an experiment that represent
different levels of the IV and are compared
Control condition: a condition that does not involve exposure to the IV, and is
compared to other experimental conditions. People assigned to the control group serve
as the basis of comparison for the people in the experimental condition
Experimental design: the way participants are allocated to levels of the IV
● Independent measures design: a different group of participants is used for
each level of the condition
● Repeated measures design: each participant performs in every level of the IV
● Matched pairs design: participants are arranged into pairs. Each pair is similar
in ways that are important to the study, and one member of each pair performs at
a different level of the IV.
, ADV: Independent measures DISADV:
● Different participants are used ● Participant variables can affect results
in each level of the IV so there if there are important individual
are no order effects differences between participants in
● Participants see only 1 level of different levels of the IV
the IV, reducing the effect of ● More participants are needed than
demand characteristics repeated measures
● Random allocation to levels of ○ May be hard to find
the IV can reduce the effects of ○ Less effective if there is a small
individual differences sample
ADV: Repeated measures DISADV:
● Participant variables are unlikely to affect ● Order effect could affect
the result as each participant does all result
levels ○ Counterbalancing
● Counterbalancing reduces order effects ● Greater exposure to demand
● Uses fewer participants than characteristics
independent measures so is good when ○ See the experimental
participants are hard to find task more than once
ADV: Matched pairs DISADV:
● Participants see only 1 level of the ● The similarity between pairs is
IV, reducing the effect of demand limited by the matching process
characteristic ○ Right matching criteria
● Participant variables are less likely must be chosen in advance
to affect the result than in to be effective
independent measures as ● Availability of matching pairs may
individual differences are matched be limited
● No order effects ○ Making the sample size
small
