Biology accurate and precise measurements?

Question

You measure 5 ml of a solution and determine its mass on a balance. You repeat this procedure four times. You try the experiment again. This time you have four new values for mass, as shown below. What is the statement that best describes the measurements?

Experiment 1: 5.7g, 5.8g, 5.7g, 5.8g
Experiment 2: 4.9g, 5.0g, 4.8g, 5.3g

a) the measurements in both experiements are accurate and precise
b) the measurements in both experiements are not accurate but are precise
c) the measurements in experiment 1 are not accurate but are precise; the measurements in experiment 2 are accurate but not precise
d) the measurements in experiement 1 are accurate and not precise; the measurements in experiment 2 are not accurate and not precise

Can I have an explanation also?

Answer 1

I vote for c.

Think of precision as how close your individual measurements within an experiment are to each other regardless of how correct (or accurate) they are.

Think of accuracy as how close you got to the correct value.

On a side note, 5 mL of an aqueous solution will weigh pretty close to 5 g.

So if 5g is the correct value, all your measurements in the first experiment are precise (because they're all very close), but not accurate because they're all pretty far away from 5.

But in the 2nd experiment the values are all close to 5, (and so accurate) but not too precise because there is some distance between the lowest value and the highest value.