Concept explainers
You set out to determine the density of lead in the laboratory. Using a top loading balance to determine the mass and the water displacement method (Study Question 41) to determine the volume of a variety of pieces of lead, you calculate the following densities: 11.6 g/cm3, 11.8 g/cm3, 11.5 g/cm3, and 12.0 g/cm3. You consult a reference book and find that the accepted value for the density of lead is 11.3 g/cm3. Calculate your average value, percent error, and standard deviation of your results.

Interpretation: The average, percent error and standard deviation has to be calculated.
Concept introduction:
Precision: Is a measurement indicates how well several determination of the same quantity agree.
Accuracy: Is the agreement of a measurement with the accepted value of the quantity.
Percent error: The difference between measured result and the accepted value.
Percent error = Error in measurementAccepted value× 100%
Error in measurement = Experimentally determined value - Accepted value.
Answer to Problem 62RGQ
The average value is 11.725 g/cm3.
The percent error obtained is 3.7%
The obtained Standard deviation is 0.19g/cm3
The average value, percent error and standard deviation is calculated as,
Explanation of Solution
Average density Value:
Average density : 11.6+ 11.8 + 11.5 + 12.04 = 11.725 g/cm3.
Hence, the average density value is obtained as shown above. Hence, the average value is 11.725 g/cm3.
Percent error:
Error in measurement = 11.725 g/cm3 - 11.3 g/cm3Percent error = 11.725 g/cm3 - 11.3 g/cm311.3 g/cm3× 100% = 3.7%
From the above calculation, the percent error is obtained as shown above.
Standard deviation:
SD =√Σ|x-μ|2Nwhere, x is values in the data set, μ is average of the data set (mean value), N is no.of data points.Given : Find mean value (μ):μ = 11.6+ 11.8 + 11.5 + 12.04 = 11.725 g/cm3.DeterminationMeasured valuesDifference between Measurement and Average(x-μ)Square of Difference|x-μ|2111.6-0.1250.016211.80.0750.006311.5-0.2250.051412.00.2750.076Σ|x-μ|2=0.016 + 0.006 + 0.051 + 0.076 = 0.149SD=√0.1494= 0.19g/cm3
The obtained Standard deviation is 0.19g/cm3
The average value was calculated as 11.725 g/cm3.
The percent error obtained was calculated as 3.7%
The obtained Standard deviation was calculated as 0.19g/cm3
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