Preventing error and bias Flashcards
what is an extraneous variable
any variable that is not the iv butt may cause an unwanted effect on the dv, they are identified at the start of the experiment
what is a cofounding variable
a variable other than the iv that has systematically affected the dv, can only be identified after the study
examples of cofounding and extraneous variables
participant related variables, order effects, placebo effects, experimenter effects, situational variables, non-standardised instructions and procedures and demand characteristics
participant related variables
the characteristics of a study’s participants that may affect the results
how to reduce participant related variables
large sample size and using random or stratified sampling rather than convenience and using a withiin subject design
order effects
the tendency for the order in which participants complete experimental conditions to have an effect on their behavior
examples of order effects
practice effects, fatigue effects and expectations
how to reduce order effects
counterbalancing
what is counterbalancing
it involves the systematic manipulation of the presentation of tthe different levels of the iv, e.g one group does a-b, the other doe sb-a
what is the placebo effect
a type of expectancy effect, where a participants expectations about the treatment/condition cause changes in their behavior
the two ways a placebo is used to control the placebo effect
- helps to equalise the expectancy across both groups, none of the study know what treatment they are getting 2. partcipants would be told that there is a placebo being used and they may/ mey not recieve it
what is a placebo
an inactive substance or treatment, the control group
do placebos stop the placebo effect
not necesarily, they help researchers understand how significantly an active intervention may affect individuals
demand characteristics
cues in an experiment that may signal to a participant the intention of the study and influence their behaviour, they are more likely to conform to the studys hypothesis and meet the studys ‘demands’
experimenter effects
the expectations of the researcher affects the results of an experiment
how to reduce experimenter effects
double blind procedures
single blind procedures
a procedure where participants are unaware of the experimental group or condition they have been allocated to
single blind procedures reduce…
participants expectations and can reduce the placebo effect
double blind procedure
a procedure where both participants and experimenter do not know which conditions or groups the participants are allocated to
what does double blind procedures reduce
prevent the experimenter effects, demand characteristics and experimenter and participant expectations
situational variables
any environmental factor that may affect the dependent variable, they can be extraneous and/or cofounding variables
examples of situational variables
temperature, lighting, weather, time of day, noise location
non-standardised instructions and procedures
occur when the directions and procedures differ across participants or experimental conditions. this introduces unwanted situational variables for either participants or entire experimenter geoups
how to reduce situational variables
standardised testing, conditions and procedures
what are standardised testing, conditions and procedures
ensuring that each participant in an experiment recieves the same instructions and follows the same procedures in each condition, sometimes the info about the true purpose of study is withheld or decieved
standardised testing, conditions and procedures reducee
extraneous variables of non-standardised instructions and procedures and allows researchers to conclusively infer that the results are due to the IV
controlled variables
variables that remain constant so that their iimpact is systematically minimised and accounted for
