Quantitative Research Methods Lecture 3

what does experimental studies look at

the effect of one variable on another and the relationship between 2 or more variables BUT the IV is manipulated

IV =…

x

DV =…

y

what is the purpose of having an experimental and control group

to have a baseline comparison

experimental group

manipulates x and measures y

control group

when all other variables remain the same

why should control and experimental groups be identical as far as possible, apart from the intentional manipulation of x (IV)

so that the researcher can isolate x → results due to that variable or to other factors

control variables 

• kept constant 

• not main variable, but can influence outcome 

• by keeping constant, we limit their influence on study results 

confounding variables

• unplanned

• can influence other variables, potentially leading to distortions in results

what is the difference between control and confounding variables

• control variables are identified early and remain constant

• confounding variables have limitation, not controlled for

what are operational definitions

information regarding what the variable is in the context of the current study

attention 

measured by the digit span test 

validity

your study accurately measures what is supposed to measure

reliability

• results are consistent

• if the study were to be repeated under the same conditions, the results would be the same