You and your lab partner are asked to determine the density of an aluminum bar.
ID: 533664 • Letter: Y
Question
You and your lab partner are asked to determine the density of an aluminum bar. The mass is known accurately (to four significant figures). You use a simple metric ruler to measure its dimensions and obtain the results for Method A. Your partner uses a precision micrometer and obtains the results for Method B.
SHOW ALL STEPS INVOLVED IN CALCULATING PLEASE!!!!!!
The accepted density of aluminum is 2.702 g/cm 3 .
(a) Calculate the average density for each method.
Should all the experimental results be included in your calculations? If not, justify any omissions.
(b) Calculate the percent error for each method’s average value.
(c) Calculate the standard deviation for each set of data.
(d) Which method’s average value is more precise? Which method is more accurate?
Method A (g/cm3) 2.7 Method B (g/cm3) 2.703 2.701 2.705 5.811Explanation / Answer
A) Average density of Aluminium calculated by Method A= 2.4g/cm3
Average density of Aluminium calculated by Method B = 2.703g/cm3
(4th measurement is omitted due to large difference with the first three values.)
B) Percentage error for Method A = Exact value-Approximate value/exact value* 100
= 2.702-2.4/2.702 * 100 = 11.17%
Percentage error for Method B = 2.702-2.703/2.702 * 100 =0%
C) Standard deviation for method A = 0.216
Standard deviation for method B = 0.002
D) Precision refers to closeness of various measurements for the same quantity.
Accuracy is the agreement of the particular value to the true value of the result.
Method A is more precise and Method B is more accurate.
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