Question Video: Determining Whether Measurements Are Precise or Accurate Chemistry • First Year of Secondary School

Video Transcript

Six measurements are shown on the scale below. The actual value being measured is 15.0. What statement uses the correct scientific words to compare the red arrows to the blue arrows? (A) The red arrows and the blue arrows are not precise measurements. (B) The red arrows are precise measurements, while the blue arrows are not precise measurements. (C) The red arrows are accurate measurements, while the blue arrows are not accurate measurements. (D) The red arrows are precise measurements, while the blue arrows are accurate measurements. Or (E) the red arrows are not accurate measurements, while the blue arrows are accurate measurements.

Let’s clear some space on screen to discuss how to compare the red arrows and the blue arrows.

All of the answer choices use the terms precise and accurate to describe the red and blue arrows. Scientific measurements are precise when they are close to each other. We can use the metaphor of a dart board to illustrate this. If three darts are thrown and hit a similar area of the board, we can consider them precise, as they are consistently close to each other. If three darts are thrown and are not close to each other, these trials would not be considered precise.

When scientific measurements are consistent but not the correct value, we may need to calibrate our equipment. This would allow our measurements to be more accurate, which means they would be closer to the true or accepted value.

For example, if darts hit the bullseye, they are accurate as they have arrived at the desired area on the board. It is possible to be precise but not accurate, as the pink darts in the diagram demonstrate. It is also possible for values to be neither accurate nor precise, which the green darts in the diagram demonstrate, meaning there is quite a lot of error in the measurements.

Let’s use this information to analyze the blue arrows on the scale. The actual value we are given in the question is 15.0. We can see that none of the blue arrows are near the true value. So the blue arrows are not accurate measurements. They are also not close to each other. So they resemble the pattern of the green darts. The blue arrows are neither accurate nor precise.

Let’s have a look at the red arrows. We can see that the red arrows are close to each other, similar to the pink darts, so they are precise measurements. None of the red arrows are near 15.0, however, so they are not accurate.

Let’s have another look at our answer choices. We can see that the only answer choice that aligns with our discussion is answer choice (B). Therefore, the statement that uses the correct scientific words to describe the red and blue arrows is answer choice (B). The red arrows are precise measurements, while the blue arrows are not precise measurements.