Question

How close a series of measurements are to each other

Answer 1

Is It Possible for a Series of Measurements to Be Accurate but Not Very Precise?
Answer
Yes, it is possible for a series of measurements to be accurate but not precise. The measurements can either be accurate, precise, neither, or both. If the measurements are both accurate and precise then it is known as valid. You can find more information here: http://en.wikipedia.org/wiki/Accuracy_and_precision

Answer 2

Hope that helps....