A student wishes to test the accuracy of the measuring jug she is using in an experiment. The label on the jug claims that it measures volume to an accuracy of plus or minus 5 cm3. The density of water is about 0.999 g cm−3, which means that 100 cm3 of water should have a mass of about 100 g. She repeatedly measures out 100 cm3 samples of water in the jug, and each time records the mass as shown in the table below:
Mass of
measuring jug :685,684,688,686,683,689,687,690,688,691
+ 100 cm3 of
water / g
Mass of
measuring jug:596,596,596,596,596,596,596,596,596,596
/ g
Mass of
100 cm3 of:89,88,92,90,87,93,91,94,92,95
water / g
Which phrase best describes these readings?
1) They are neither precise nor accurate
2) They are relatively precise but not accurate
3) They are relatively precise and relatively accurate
3 correct answer or not plz help
To determine the best phrase that describes the readings, we need to understand the concepts of accuracy and precision.
Accuracy refers to how close the measured value is to the true or expected value. In this case, the expected mass of 100 cm3 of water is about 100 g.
Precision, on the other hand, refers to how close the measured values are to each other. It indicates the consistency or reproducibility of the measurements.
Looking at the table, we can compare the recorded masses of the measuring jug when empty. The readings are consistently around 596 g, which suggests a relatively precise measurement.
However, when the 100 cm3 of water is measured, the recorded masses are more varied, ranging from 87 g to 95 g. This indicates a lack of accuracy since the expected value is around 100 g.
Based on these observations, the correct answer is 2) They are relatively precise but not accurate.