1. Research MethodsResearch Methods
Aqa A PsychologyAqa A Psychology

2. In this power point:In this power point:
 VariablesVariables
 Types of experimentTypes of experiment
 Group designsGroup designs
 Types of hypothesisTypes of hypothesis
 Types of samplingTypes of sampling

3. VariablesVariables
 TheThe independent variableindependent variable is that theis that the
experimenter manipulates…experimenter manipulates…
 ……in order to investigate whether there is ain order to investigate whether there is a
change in thechange in the dependent variabledependent variable
 TheThe dependent variabledependent variable is what theis what the
experimenter measuresexperimenter measures
 ConfoundingConfounding oror extraneous variablesextraneous variables areare
unwanted other potentially interveningunwanted other potentially intervening
variablesvariables

4. Types of experimentsTypes of experiments
3 Types:3 Types:
 LaboratoryLaboratory
 FieldField
 Quasi / naturalQuasi / natural

5. LaboratoryLaboratory
+ high levels of control to limit confounding+ high levels of control to limit confounding
variablesvariables
+ easy replication to check results,+ easy replication to check results,
increasing reliabilityincreasing reliability
- may cause demand characteristicsmay cause demand characteristics
- Low ecological validityLow ecological validity

6. FieldField
+ natural experiment makes for high+ natural experiment makes for high
ecological validityecological validity
+ Pp’s are unaware that they’re being+ Pp’s are unaware that they’re being
studied so no demand characteristicsstudied so no demand characteristics
- extraneous variables can effect the resultsextraneous variables can effect the results
- because Pp’s don’t know they’re beingbecause Pp’s don’t know they’re being
studied they cannot give their full informedstudied they cannot give their full informed
consent so ethical issuesconsent so ethical issues

7. Quasi / NaturalQuasi / Natural
+ it is possible to study relationships that+ it is possible to study relationships that
cannot be directly measured without itcannot be directly measured without it
being unethical e.g. the effects of capitalbeing unethical e.g. the effects of capital
punishment on serious crimepunishment on serious crime
- there is no control over confounding- there is no control over confounding
variables so it is hard to identify casualvariables so it is hard to identify casual
factorsfactors

8. Group designs
3 Types you should know
 Independent group design
 Repeated measures design
 Matched pair design

9. Independent
Different Pp’s are used in each condition of
the experiment
+ no order effects
- participant variables differ between
conditions
- there is a need for more Pp’s

10. Repeated
Same Pp’s are used in each condition of the
experiment
+ there is a need for fewer Pp’s
- risk of order effects
- practice or fatigue effects

11. Matched pairs
Each participant is matched on all variables that are
considered to be relevant to the investigation with a
Pp in another group or condition
+ limits some effects of the Pp variables
- matching Pp’s can be difficult and time consuming

12. Hypothesis
Directional hypothesis-
used when previous research suggests what the
outcome is going to be
Non-directional hypothesis-
used when we cannot be certain what the results will
show
Null hypothesis-
this assumes that there will be no effect in the same
population by which the samples are drawn

13. Types of samplingTypes of sampling
There are 4 types you should knowThere are 4 types you should know
► Random samplingRandom sampling
► Opportunity samplingOpportunity sampling
► Self-selected samplingSelf-selected sampling
► Stratified samplingStratified sampling

14. RandomRandom
e.g. pulling a name out of a hat or using a computere.g. pulling a name out of a hat or using a computer
to get a random sampleto get a random sample
+ it is mathematically unbiased+ it is mathematically unbiased
- risk of skewed sample despite it being- risk of skewed sample despite it being
mathematically unbiasedmathematically unbiased
e.g. the lottery may still picke.g. the lottery may still pick
8-9-10-11-12-138-9-10-11-12-13

15. OpportunityOpportunity
e.g. asking people around you that are readye.g. asking people around you that are ready
and availableand available
+ it is quick and convenient+ it is quick and convenient
- the sample will be biased so- the sample will be biased so
unrepresentativeunrepresentative

16. Self-selectedSelf-selected
e.g. volunteerse.g. volunteers
+ your Pp’s will be motivated+ your Pp’s will be motivated
- personality biased as they all share the- personality biased as they all share the
same interest in volunteeringsame interest in volunteering

17. StratifiedStratified
e.g. choose 10% from each countrye.g. choose 10% from each country
or 10% from each classor 10% from each class
+ an effort is made to get a representative+ an effort is made to get a representative
samplesample
- it is very time consuming- it is very time consuming