staged manipulations frequently employ a confederate or an accomplice. Usually the
confederate appears to be another participant. They are useful in creating a particular
Eg in a study on aggression, the confederate and the participant
Research on Expectancy Effects
the earliest demonstration was the case of Clever Hans (a clever horse who could pick up
on his masters very subtle facial expressions to respond a certain way) in 1911. If a horse
can do it, so can humans!
Can be communic
Researchers must be extremely careful not to invade participants privacy and that
confidentiality is maintained.
The basic experimental design has two groups: in the simplest case, an experimental
group which receives manipula
Behavioural measures are direct observations of behaviour.
Like self-reports, there are almost an endless number of measures of behaviour possible.
Researcher may record whether or not a specific behaviour occurs eg whether or not
This is an attempt to directly measure whether the independent variable
manipulation had the intended effect on the participants, providing evidence for the
construct validity of the manipulation
Eg. If you were manipulating anxiety,
Increasing the Number of Levels of an Independent Variable
In the simplest experimental design there are only two levels of the independent
However, a researcher may want to design an experiment with three or more levels
for several reasons:
If behaviour changed when the treatment is introduced then reversed when the treatment
is removed, it is evidence for effectiveness of the treatment
Some treatments do not produce an immediate effect, but the single case design can be
appropriate for the
Increasing the Number of Independent Variables in a Factorial Design
we can also increase the number of independent variables in a factorial design.
a 2 x 2 x 2 factorial design has 3 independent variables, each with two levels
thus, there are 8 condit
Interactions and Simple Main Effects
Analysis of Variance a process used to assess the statistical significance of the
main effects and the interaction in a factorial design.
When there is a difference, there is a need to statistically evaluate the indivi
These main effects tell us that overall there are more errors when the questioner is
knowledgeable and when the questions are misleading, but there is also the possibility
that an interaction exists; if so, the main effects of the independen