Accuracy and Precision Self-Quiz 1 ... measurement is both accurate and ... Wendy is using a poorly calibrated electronic balance to measure the mass ...

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Accuracy and Precision Self-Quiz 1. Define accuracy.

2. Define precision.

3. John measures the mass of a rock and finds it to be 12.21 kg. He states that his measurement is both accurate and precise. For what two reasons is his statement incorrect?

4. Wendy is using a poorly calibrated electronic balance to measure the mass of a crucible. Her technique in making the measurement is very careful and she repeats it three times. What will likely characterize her measurements? a) high accuracy and high precision b) high accuracy and low precision c) low accuracy and high precision d) low accuracy and low precision

Refer to the following experiment to answer questions 5-7. Three students have made multiple measurements of the solubility of sodium chloride (in g of NaCl per 100 g of water). Their results are summarized in the table below. The correct value for the solubility of sodium chloride is 35.9 g.

Nicole Matthew Leonard

Trial 1 35.4 g 31.8 g 39.2 g

Trial 2 36.1 g 34.1 g 39.3 g

Trial 3 35.7 g 41.5 g 38.9 g

5. Which student’s measurements have high precision but low accuracy? a) Nicole b) Matthew c) Leonard 1

6. Which student’s measurements are both accurate and precise? a) Nicole b) Matthew c) Leonard

7. Calculate the average of Matthew’s three measurements. Comment on his accuracy and precision.

Refer to the following experiment to answer questions 8-10. Kaitlyn makes three determinations of the density of aluminum. She obtains 2.72 g/mL, 2.86 g/mL, and 2.64 g/mL, which results in an average of 2.74 g/mL for her three measurements. 8. The deviation of a measurement is defined as the absolute value of the difference between that particular measurement and the average value. Deviation = |measured value – average value| Calculate the deviations for each of Kaitlyn’s density measurements.

9. The average deviation is the sum of each individual deviation divided by the total number of measurements. Calculate the average deviation for Kaitlyn’s experiment.

10. What conclusion can be drawn from an experiment in which the average deviation is very small? a) The measurements are accurate. b) The measurements are precise. c) The measurements are both accurate and precise. d) No conclusions about either accuracy or precision can be made.

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