Explain whether there is likely to be variability in the following measurements if they were to be taken on 10 consecutive days for the same student. If so, explain whether the variability most likely would be due to natural variability across time, natural variability across individuals, measurement error, or some combination of these three causes.

*a. Systolic blood pressure

*b. Blood type (A, B, O, AB)

c. Time on the student’s watch when the actual time is 12 noon

d. Actual time when the student’s watch says it’s 12 noon