Because the measurement usually requires putting the measurement device in the experiment. Just observing an experiment effects it because you are interpreting the results.
A cohort is a sample of people that are all born at about the same time. For instance, everyone that you are studying are born in 1940. Time measurement effects mean when the time you measure...
definitely. the manner by which you wrap the cuff on the person's arm determines the accuracy of the measurement of BP. if you wrap it too tightly you will get false high results. if you wrap it...