hypothesis
a testable prediction about the results of a study
null hypothesis
a statement that there is no statistical significance between the variables in a study; this is what the researcher tries to statistically disprove
population
the entire group that a researcher is studying
representative sample
a small group which shares characteristics with the population being studied
random sample
a group of subjects to be studied selected with no pattern
random placement
placing subjects into the experiment or control groups with no pattern
operational definition
a procedure for identifying and measuring variables in a study; required for other researchers to replicate the experiment
independent variable
the variable that is manipulated by a researcher in a study; usually expected to have an effect on other variables
dependent variable
the variable that is measured in a study; usually expected to change across groups/trials
confounding variable
any variable that cannot be entirely controlled/eliminated
experimental control
strategies implemented by a researcher to reduce the effect of confounding variables
experimental group
group that is exposed to the independent variable
control group
group that is not exposed to the independent variable
placebo group
group that receives a fake treatment; mostly used in drug trials
single blind study
study in which subjects do not know which group they are in
double blind study
study in which neither the subjects nor the researcher know which group is receiving the treatment; prevents bias in interpreting the data
p-value
a statistical measurement that indicates how likely it is that an observed relationship between variables is due to chance; can never be a negative value; if this value is less than 0.05, reject the null and accept the hypothesis