How can results from an experiment be precise but not accurate?

Question

please someone answer!!!

Answer 1

One example is if the tool you are using to measure something is not calibrated properly you will get consistent, but wrong answers.

For example, if your ruler is not spaced properly and you measure something 100 times, you'll get the same value each time --> thus your experiment was precise. However, if you compare this value to the actual value, it will be way off (and thus not accurate).

Answer 2

Think of it this way in terms of a math problem:

What is 2 + 2?

You know the answer is 4 (that is accurate and precise)

If try answering the question 100 times and keep getting the answer to be 5, then the answer is precise (it is repeatable), but not accurate (since you know the actual answer is 4). If you answer the question and get 100 different answers that vary from 0 to 8, then the answer is neither accurate (4) nor precise (repeating). If those 100 answers average to 4, then the average is accuarte, but not precise.

I typically use a dartboard analogy when trying to explain this as well. Think of trying to hit the bull's eye (accurate and precise). If you throw and hit all over the board, but average out to the bull's eye (in terms of location), then you are accurate on average, but not precise. If you keep hitting the outer ring on the 20, then you are not accurate, but you are precise.

I hope this helps.

Answer 3

It can give you the wrong answer to 17 decimal places. A practical example would be a scale calibrated for use at the equator being used in Oregon - the scale will continue to be as precise as it always was, but it will consistently report a mass in excess of the actual mass of the object being weighed, because of the slight difference in the local gravitational field*. This effect is large enough that scale manufacturers must calibrate the scales differently for each locale in which they might be used.

*Just in case you're curious, the reason this difference exists is because the Earth is an oblate spheroid, places closer to the poles are slightly closer to the center of the Earth and as such have more gravity. Also, since what is measured by scales is not the actual gravitational force, but the normal force required to keep the object from falling through the scale, and since objects nearer the equator have more angular momentum helping to keep them at the same distance from the Earth's center, the normal force required at the equator is less than the total gravitational force. The practical effect of both of these phenomena is that an object will be slightly heavier in the temperate zones than near the equator, and as such a scale calibrated for the equator which is used in Oregon will consistently report a mass that is too large.

Answer 4

Many of the answers posted for this question appear to confuse "precision" with "consistency." Maybe the word "precise" has taken on this new meaning in lab sciences during the years since I left school, but I think the correct answer to your question is:

"Precise" refers to the degree of exactness with which a value is stated. For example, the number 3.1415926536 is very "precise" because it has many significant digits. It is a very exact statement of a value, in this case the value of pi. This number is also very "accurate," since this is the actual value of pi (to 10 or 11 significant digits).

If I had stated that the value of pi is 2.3415926536, that would again be a very "precise" value. In fact, it contains the the same number of "significant" digits as the value mentioned above, so it is equally precise.

However, this second number is a much less "accurate" value for pi than the one given above. It is precise, but not accurate.

In short, precision has to do with exactness; accuracy has to do with correctness.

Answer 5

Easy, if the setup of the experiment is wrong. You will get consistently wrong results. The results is precise. But the result is not accurate.

Answer 6

well, if u do the same experiment 3 times and get results that vary but are still close to each other like say, 13.5s, 13.6s, 13.4s,
those results are precise. But they are not accurate cuz to be accurate, they need to be exactly like the theoretical answer.

You can study gravity and get results like 9.92,9.87,9.85. These are precise. But if you got it 9.81, that's when your result is accurate.

Answer 7

Precision has to do with the "spread" of the data, whereas accuracy is based on how close the average value of the data points is to the "correct" value.

The analogy I like the most deals with darts on a dart board;

Imagine 4 darts are thrown and land on the dart board tightly clustered between the edge of the board and the bulls-eye at the center. This represents precision but not accurate.

Now imagine 4 darts uniformly spread around the bull-eyes but none on the bulls-eye. This represents accuracy but poor precision.

Now imagine the last example but bring the darts closer to the bulls-eye, if not on it. This represents accuracy with increasing precision.

Answer 8

you could use a ruler to measure something on your desk. You could position it in an unstable position, move while you take the measurement, not be careful in any way.

You could still end up with a very precise number, say 2.642 inches. But it would not be accurate because you were careless.

Answer 9

You could come up with an answer such as 10 divided by 2 = 4.9999999999

Very precise, but wrong.

Answer 10

Results are precise if there is little variation between them (their standard deviation is relatively small) This, however, does not always imply that the mean result agrees with proven standards.