Definitions
What does accuracy refer to in laboratory measurements?
The closeness to the true value.
Differentiate between accuracy and precision using an example.
Accuracy is hitting the center of a target, while precision is hitting tightly grouped shots, even if they're not centered.
This is the equation for Percent Error.
What is (experimental - accepted) / accepted * 100
Average = 45.68 g
Actual = 100g
Not accurate
Range 0.52?
Precise
What term refers to the degree of consistency and reproducibility of measurements?
Precision
Provide an example illustrating precision without accuracy.
Throwing a series of darts that are closely grouped but consistently away from the bullseye on a target board. (just an example)
Experimental Value = 62.5 g. Accepted Value = 65.2 grams.
What is 4.14% error?
Data points = 23, 56.7, 25.5, 32, 30, 15
Actual = 30
average - 30.37
Accurate
Data points = 23, 56.7, 25.5, 32, 30, 15
range - 20.85
Slightly precise
What is the percent error definition?
Being able to look at the percent difference between average and the actual
Describe a scenario where accuracy is achieved without precision.
The archer consistently hits the same spot outside the bullseye but at the same distance from it. This represents high accuracy (the arrows consistently hit a specific point) but low precision (the arrows are not clustered together).
This is the percent error of an experimental value of .156 cal/g and accepted value of .185 cal/g.
What is 15.68% error?
Data points - 73, 75, 68, 131, 86, 50, 39
Actual - 112
Average - 74.57
Not accurate
Data points - 73, 75, 68, 131, 86, 50, 39
range - 46
Not precise
What is the biggest difference between accuracy and precision?
Accuracy - average
precision - close to group
Provide an example illustrating precision and accuracy together.
Imagine a marksman consistently hitting the center of a bullseye (precision) and the center of the target being the true intended point of impact (accuracy).
This is the percent error of an accepted value of 34.1 mL and experimental value of 34.58 mL.
What is 1.41% error?
Data points: 1.2, .25, .37, 1.34, 1.2, .56, .73, 1.02
Actual = .50
average = 0.83
Slightly Accurate
Data points: 1.2, .25, .37, 1.34, 1.2, .56, .73, 1.02
Range = 0.545
Precise
What term describes the variability of measurements due to unpredictable factors, resulting in fluctuations around an average value?
Error
Explain a situation where data points are scattered both away from the true value and from each other, illustrating low accuracy and low precision.
The archer's arrows are scattered widely around the target, with no consistent point of impact and no clustering. This showcases both low accuracy (the arrows don't hit the bullseye) and low precision (the arrows are not grouped together).
This is the percent error of an experimental value of 97.5 degrees and an accepted value of 100 degrees.
What is 2.5% error?
Data: 1.11, 1.12, 1.14, 1.15, 1.24, 1.27, 1.33, 1.88, 1.67, 1.45, 1.22
Actual - 1.34
Average - 1.325
Accurate
Data: 1.11, 1.12, 1.14, 1.15, 1.24, 1.27, 1.33, 1.88, 1.67, 1.45, 1.22
Range - 0.385
Precise