(Year 1&2)
Year 1
Control of Variables –
The IV is manipulated to see the change in the DV. The IV should be the only thing to
influence the changes on the DV. Any other variables should be controlled and removed.
These are called extraneous variables and are also known as “nuisance” variables.
Extraneous Variables – A variable which could have an effect on the dependent variable.
This is controlled so that it does not become a confounding variable.
Confounding Variable – A variable that has an unintentional effect on the dependent
variable. When carrying out experiments we attempt to control extraneous variables,
however there is always the possibility that one of these variables is not controlled and if
this effects the dependent variable in a systematic way we call this a confounding variable.
o Participant Variables – Individual differences between participants. E.g. Levels of
intelligence, age, gender, social class and fitness.
o Situational Variables – Outside influences on the experiment. E.g. Time of day,
weather, noise and place.
o Confounding Variables – These change systematically with the IV. These could be
totally accidental, however end up changing the outcome.
Demand Characteristics – These are cues from the researcher or from the situation. This
may be interpreted as revealing the purpose of the investigation. These can include guessing
the aim of the study or giving the answer that they think the researcher wants to hear. This
is known as the “screw you” effect. This means that the behaviour is no longer “natural” and
will affect the results of the investigation.
Investigator/Experimental Effects – This is where researchers unconsciously influence the
results of the research. This includes the way participants are chosen and the instructions
given.
Single blind procedures – These can reduce demand characteristics. This is where the
participants have no idea which condition they are in.
Double blind procedures – Neither the participant or the investigator know which condition
they are in. They are both “blind” to the knowledge. This prevents any unconscious cues or
bias.
Standardisation – This involves ensuring that all participants are subject to the exact same
environment, information and experience.
Aim – An aim is a general statement of what the researcher intends to investigate. The
purpose of the study.
Aims and hypothesis – Aims are general statements that describe the purpose, whereas the
hypothesis is clear, precise statements that predict the outcome of the study.
Original Author – P E McLeod