Worksheet-Accuracy and Precision-Final (1)

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Fortis Institute, Port Saint Lucie *

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GMAS125

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Statistics

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Feb 20, 2024

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docx

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Science, Measurement, and Uncertainty: Accuracy and Precision Name: Kayla A. De La Cruz Period:1 Date: 9/7/23 ACCURACY AND PRECISION Definitions: Accuracy – how close a measurement is to the goal or target. Precision – how close a measurement is to each other. Precision versus Accuracy: Look at each target and decide whether the “hits” are accurate, precise, both accurate and precise, or neither accurate nor precise: (Note: An accurate “hit” is a bulls eye!) Accurate?: Yes / No Precise?: Yes / No Accurate?: Yes / No Precise?: Yes / No Accurate?: Yes / No Precise?: Yes / No Precision Problems: A group of students worked in separate teams to measure the length of an object. Here are their data: Team 1 Team 2 Team 3 Team 4 Team 5 Team 6 Team 7 2.65 cm 2.75 cm 2.80 cm 2.77 cm 2.60 cm 2.65 cm 2.68 cm The average length is 2.7 cm. This is the mean or average. Subtract the highest value from the lowest value: 0.15 cm. This is the range or spread. Divide this number by 2: 0.075 cm. This is the approximate ± range from the average. The precision of the measurement can be shown as average ± range.The precision of the measurement was 0.15 ± 0.075 cm. Expressing Errors in Measurement: Demystifying Scientific Data: RET 2006, Rev 2 25
Science, Measurement, and Uncertainty: Accuracy and Precision Scientists often express their uncertainty and error in measurement by giving a percent error. The percent error is defined as: % error = actual value measured value x 100 Actual value Answer the following four questions. Pay attention to significant figures, and show your work! 1. While doing a lab, a student found the density of a piece of pure aluminum to be 2.85 g/cm 3 . The accepted value for the density of aluminum is 2.70 g/cm 3 . What was the student's percent error? 2.7-2.85/2.7 x 100 2.7-2.85=-0.15 -0.15/2.7= 0.055555 -0.0555x100= -5.5% 2. A student measured the specific heat of water to be 4.29 J/g · C o . The literature value of the specific heat of water is 4.18 J/g · C o . What was the student’s percent error? 4.29-4.18/4.29 x 100 4.29-4.18=0.11 0.11x100=1.21% Precent error: 1.21% 3. A student took a calibrated 200.0 gram mass, weighed it on a laboratory balance, and found it read 196.5 g. What was the student’s percent error? 200-196.5/200x100 200-196.5 =3.5 3.5/200=0.0175 0.0175x100=1.75% Precent error:1.75% Demystifying Scientific Data: RET 2006, Rev 2 26
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