2. research issues

what are EVS

• any variable other than the IV that may affect the dependant variable if it is not controlled

• essentially nuisance variables that do not vary systematically with the IV

examples of EVs

participant age, lighting in a lab, participant reactivity (demand characteristics)

what are CVs

a type of EV but they vary systematically with the IV - means you cannot tell if any change in the DV is due to the IV or a CV

examples of CVs

different times of day, investigator effects (if diff for the diff groups), task difficulty

what are demand characteristics

• any cue from the researcher or research situation that may be interpreted by participants as revealing the purpose of the investigation

• may lead to a participant changing their behaviour within the research situation

what can demand characteristics lead to

1. please u effect - act in a way they think is expected or over perform to please the experimenter

2. screw u effect - may deliberately under perform to sabotage the results of the study

what are investigator effects

• any effect of the investigators behaviour (conscious or unconscious) on the research outcome (the DV)

• may include everything from the design of the study to the selection of, and interaction with, participants during the research process - eg leading questions

how can researchers ensure control

1. randomisation

2. standardisation

3. random allocation

4. counterbalancing

SPEC

what is randomisation

the use of chance methods to control for the effects of bias when designing materials and deciding the order of experimental conditions

what is standardisation

using exactly the same formalised procedures and instructions for all participants in a research study

what does standardisation include

standardised instructions - means changes in procedure do not act as an EV