Experimental Method
Hypothesis – a precise, testable
statement of what the researchers • The experimental method involves the manipulation of
predict will be the outcome of the variables to establish cause and effect relationships.
study. • Key features:
Directional Hypothesis - states the o controlled methods
direction (positive/negative) of the o the random allocation of participants into
difference or relationship controlled and experimental groups.
Non-directional Hypothesis – the
• In an experiment, an independent variable (the cause)
independent variable will have an
is manipulated and the dependent variable (the effect)
effect on the dependent variable,
is measured; any extraneous variables are controlled.
direction of the effect is not
specified. It just states that there will
be a difference.
Operationalisation – clearly defining • Directional hypothesis is used when a theory/findings
variables in terms of how they can of previous research suggests a particular outcome.
be measured • Non-directional is for when there isn’t any theories or
just contrasting findings
Independent variable = the cause, effects dependent variable
Dependent variable = the effect, value depends on changes to the independent variable
Operationalisation is good for making variables more measurable in case they are not
easy to define
Research Issues
Extraneous + EV – any variable (apart from independent) that may affect
confounding dependent variable
• May make it more difficult to detect an effect in
variables
experiment
CV – like EV but has to relate to independent variable
• changes systematically with IV so can’t be sure if a
change in the DV is due to the CV/EV
Demand a subtle cue that makes participants aware of what the
characteristics experimenter expects to find or how participants are expected to
behave.
Investigator Any effect of the investigator’s behaviour on the outcome of the
Effects research + design decisions
Randomisation the use of chance to prevent bias when deciding experiment
Standardisation using exact formalised materials/instructions in experiment
,
Hypothesis – a precise, testable
statement of what the researchers • The experimental method involves the manipulation of
predict will be the outcome of the variables to establish cause and effect relationships.
study. • Key features:
Directional Hypothesis - states the o controlled methods
direction (positive/negative) of the o the random allocation of participants into
difference or relationship controlled and experimental groups.
Non-directional Hypothesis – the
• In an experiment, an independent variable (the cause)
independent variable will have an
is manipulated and the dependent variable (the effect)
effect on the dependent variable,
is measured; any extraneous variables are controlled.
direction of the effect is not
specified. It just states that there will
be a difference.
Operationalisation – clearly defining • Directional hypothesis is used when a theory/findings
variables in terms of how they can of previous research suggests a particular outcome.
be measured • Non-directional is for when there isn’t any theories or
just contrasting findings
Independent variable = the cause, effects dependent variable
Dependent variable = the effect, value depends on changes to the independent variable
Operationalisation is good for making variables more measurable in case they are not
easy to define
Research Issues
Extraneous + EV – any variable (apart from independent) that may affect
confounding dependent variable
• May make it more difficult to detect an effect in
variables
experiment
CV – like EV but has to relate to independent variable
• changes systematically with IV so can’t be sure if a
change in the DV is due to the CV/EV
Demand a subtle cue that makes participants aware of what the
characteristics experimenter expects to find or how participants are expected to
behave.
Investigator Any effect of the investigator’s behaviour on the outcome of the
Effects research + design decisions
Randomisation the use of chance to prevent bias when deciding experiment
Standardisation using exact formalised materials/instructions in experiment
,
