Karissa is conducting an experiment on the amount of salt that dissolves in water at different temperatures. She repeats her tests several times using the same procedure. What can Karissa do to further increase confidence in the results of her experiment?

1) have another scientist run the same exact procedure in her lab.
2) include several other liquids for comparison.
3) calculate the average amount of salt that dissolves to summarize findings.
4) make sure the experiment follows a specific procedure that allows other scientists to produce the same findings.