example that is related exactly like one another it will mental groups except that the variable if not applied to it is a(n)?

a.observation
b.variable
c.control
d.hypothesis

after a researcher has stated the pacific problem to be studied in an experiment he or she must then develop a(n)?

a.conclusion
b.hypothesis
c.summary of the data
d.theory

which should be determined first before starting an experiment

a.materials
b.questions
c.methods
d.purpose​