Experiments- research methods Flashcards
Independent Variable
Independent Variable (IV): a feature of the experiment that is manipulated by the researcher in order to observe whether a change occurs in the dependent variable (DV)
Dependent Variable
Dependent Variable: result of that manipulation. The experimental variable that is measured by an experimenter
Level of significance
Level of significance: this indicates the extent to which a set of results are due to chance factors alone rather than the independent variable (I.V)
Laboratory experiments
the IV is manipulated by the researcher and the experiment is carried out in a laboratory or other contrived setting away from the participant’s normal environment
Field experiments
the IV is manipulated by the researcher but this time the experiment is carried out using participants in their normal surroundings
Quasi (or natural) experiments
the IV is naturally occurring (e.g. cloudy conditions versus sunny conditions; morning versus afternoon), not manipulated by the researcher
Advantages of lab experiment
Standardised procedure (same materials for all ps so it’s consistent-reliability)
Control of extraneous variables-validity
disadvantages of lab experiment
High risk of DC(usually)-construct validity
Low ecological validity- doesn’t reflect real life
advantage of a field experiment
Field experiments can offer a more realistic
setting for a study, and therefore can have
more ecological validity
disadvantage of a field experiment
Lack of control can mean it is difficult to
assume that the variable manipulated was actually influencing behaviour and that it wasn’t something else.
Repeated measures Design
this involves using the same people in each condition
Independent Measures Design
this involves using different people in each condition
Matched groups design
this involves using different people in each condition but an attempt is made to make the participants as similar as possible on certain key characteristics (any that might influence the findings). This is done by testing the individuals on the key characteristics, pairing them based on similar scores, and then placing one member of each pair into each group.
Extraneous Variables:
a variable that if they are not controlled they may obscure the effect of the I.V. If this happen then it becomes a confounding variable
An alternative hypothesis
This predicts how one variable (the IV) is likely to affect another variable (the DV). An alternative hypothesis predicts that the IV will affect the DV.
A null hypothesis
This predicts that the IV will not have an effect on the DV. The null hypothesis predicts that any difference seen will be due to chance factors rather than the independent variable.
Two tailed
This predicts that the IV will have a significant effect on the DV (i.e. there will be a significant DIFFERENCE in the results from the different conditions of the experiment), but it does not predict the direction this effect will go in.
One Tailed
This predicts not only that the IV will have a significant effect on the DV but also the direction this effect will go in (i.e. the kind of difference – more or less, quicker or slower – between the conditions of the experiment).
advantages of mean
easy to calculate
presents central point of distribution curve
disadvantage of mean
may not be representative of any scores in the data
affected by extreme scores
advantage of median
Not affected by extreme scores
disadvantage of median
Can be distorted by small samples
advantage of mode
Not influenced by extreme scores
It is the only measure which can deal with non-numerical data (tally frequency on observations). For example the most frequent eye colour in this group.
disadvantage of mode
Not useful if many equal modes
Range
is a measure of how spread
out your data is
Variance
measures how much a set of numbers is spread out. On its own, it gives an idea of how spread scores are from the mean. It comes into use when calculating the standard deviation