How to Measure Properly

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Presentation transcript:

How to Measure Properly

The line falls between 23.1 and 23.2 Closely The line falls between 23.1 and 23.2

The measurement extends between 23.1 and 23.2 23.1?

Therefore, we can be sure the measurement is 23.1? This is where “estimation” comes into play…

Uncertainty in Measurements Person 1 2 3 4 5 Measurement (cm) 1.25 1.26 1.24 1st two numbers (1.2_) are certain. Last number is (1.2?) uncertain.

Every measurement REQUIRES only 1 estimation!!!

Significant Figures Practice Determine the number of significant figures in… 3.05 g

Significant Figures Practice Determine the number of significant figures in… 3.05 g 3 Sig figs!

Significant Figures Practice Determine the number of significant figures in… 600 g

Significant Figures Practice Determine the number of significant figures in… 600 g 1 Sig fig!

Significant Figures Practice Determine the number of significant figures in… 0.9280 s

Significant Figures Practice Determine the number of significant figures in… 0.9280 s 4 Sig figs!

Significant Figures Practice Determine the number of significant figures in… 0.0006 mm

Significant Figures Practice Determine the number of significant figures in… 0.0006 mm 1 Sig fig!

Significant Figures Practice Determine the number of significant figures in… 5000 kg

Significant Figures Practice Determine the number of significant figures in… 5000 kg 1 Sig fig!

Significant Figures Practice Determine the number of significant figures in… 3.0 x 10 m/s 8

Significant Figures Practice Determine the number of significant figures in… 3.0 x 10 m/s 2 Sig figs! 8

Significant Figures Practice Round each value to two significant figures. 78.9 m

Significant Figures Practice Round each value to two significant figures. 78.9 m  79 m

Significant Figures Practice Round each value to two significant figures. 135947 km

Significant Figures Practice Round each value to two significant figures. 135947 km  140000 km Or 1.4 x 10 km 5

I have a splitting headache… Accuracy vs. Precision I have a splitting headache… Completely missed the dartboard!!!

Accuracy Refers how close a measurement is to the actual (true) value. Dartboard Analogy: The bull’s eye is the actual point where a person is aiming for. 100g

Accurate “correct”. A measurement is considered accurate if correctly reflects the size of the object being measured. How close are you to the actual/accepted value? Does the practice of using body parts as measurement tools produce accurate results?

Precision Refers how close a a group of measurements are to one another. (reproducibility) Person 1 2 3 4 5 Measurement (cm) 1.25 1.26 1.24

Precise A precise measurement is repeatable and reliable. Getting the same measurement each time. Does the practice of using body parts as measurement tools produce precise measurements? (were all of your results the same?)

Accurate or precise? Accurate and Precise!

Accurate or Precise? Accurate

Accurate or Precise? Accurate

We can never get a perfect measurement, the best that we can do is get as close as possible within the limitations of our measuring instruments.

Every measurement REQUIRES only 1 estimation!!!