control of variables Flashcards
what is an extraneous variable
the key to an experiment is that an independent variable (IV) is manipulated (changed) to see how this affects the dependent variable (DV)
Essentially, the only thing that should influence the DV is the IV and any other variables that interfere with the IV or the DV should be controlled or removed
These additional, unwanted variables are called extraneous variables
what are some examples of extraneous variables
examples of extraneous variables are:
- lighting in the lab
- age of the participants
therefore, many extraneous variables are easy to control
how do extraneous variables vary with the IV
extraneous variables do not vary systematically with the IV -
they “muddy” the experimental water but for not confound the findings of the story. They may just make it harder to detect a result
how do confounding variables vary with the IV
confounding variables vary systematically with the IV
Essentially, confounding variables create a second IV
e.g.
in our energy drink study we have twenty participants in total and decide to use the first ten participants who arrive for the water condition
- these participants are shy, introverted individuals
- the other condition participants are extraverted
This would create an unintentional second IV - personality
Therefore when we come to analyse our data and find that the other group was chattier, we can’t be sure if this is because of the drinks or the personality of the participants
what is an example of a confounding variable
personality is a confounding variable
e.g. for the examples shown on the previous card, the problem was that extraversion varied systematically with the IV and thus alone could explain changes in the DV
what are demand characteristics
demand characteristics are certain cues that may help participants interpret what is going on in an experimental situation
These cues can help participants to “second - guess” the experimenter’s intentions as well as the aims of the study
why are demand characteristics hard to control
participants reactivity is a significant extraneous variable in experimental research and one that is very difficult to control
what do demand characteristics lead to
demand characteristics may lead to:
- participants may look to clues to tell them how they should behave in the experiment.
This cloud lead to participants over performing to please the experimenter or deliberately “under- performing” to sabotage the results in the study
Either way, the participants behaviour is no longer natural and is an extraneous variable that may affect the DV
what are investigator effects
participant reactivity also leads to investigator effects
e.g.
It is possible that during our energy drink experiment, as we are recording the words spoken by each participant, we may be inclined to smile more during out interactions with some of the participants ( we as in the experimenter)
Given that we are expecting thee energy drink group to speak more than the water group, we may unknowingly - in our unconscious behavior- encourage a greater level of chattiness from the energy drink participants
Basically, investigator effects refers to any actions of the researcher that were related to the study’s design. This includes expectancy effects and unconscious cues e.g. selection of the participants, the materials, instructions - leading questions
what is randomisation
there are many steps that the researcher can take to minimise the effect of extraneous/ confounding variables on the outcome
one of these steps is randomisation
Randomistation refers to the use of chance wherever possible to reduce the researcher’s influence on the design of the investigation.
This is an attempt to control investigator effects
what is standardisation
as far as it is possible, within an investigation, all participants should be subject to the same environment, info and experience
to ensure this, all procedures are standardised in other words there is a list of exactly what will be done in the study. This includes standardised instruction that are read to eac participants
Such standardisation
means that non - standardised changes in procedure do not act as extraneous variables
