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PERCENT PERCENT ERROR, ERROR,
ACCURACY VS. ACCURACY VS. PRECISION PRECISION
AND AND MEASURMENTMEASURMENT
PERCENT ERRORPERCENT ERROR
Your Measured Value – Actual ValueYour Measured Value – Actual Value
Actual ValueActual Value XX 100100
Absolute Value Absolute Value sign: the sign: the
difference difference cannot be cannot be negativenegative
Problem #
Basic Equation Working Equation
Given variables Solve
Answer3 Sig figsSci Not. Units
Rectangle of Power!Rectangle of Power!
Making sure you subtract the mass of the box, you re-Making sure you subtract the mass of the box, you re-measure the mouse and determine its real mass as 15.0 measure the mouse and determine its real mass as 15.0 grams. What is the percent error?grams. What is the percent error?
Example:Example:
You measure the mass of a mouse to be 14.6 grams. But You measure the mass of a mouse to be 14.6 grams. But because it is constantly jumping around you are not sure because it is constantly jumping around you are not sure if you made an accurate measurement.if you made an accurate measurement.
SO:SO:
*No real mice were hurt in this example.*No real mice were hurt in this example.
Problem # Example
Basic Equation Working Equation
Given variables Solve
Answer3 Sig figsSci Not. Units
Rectangle of Power!
(M-A)/A x 100 (M-A)/A x 100
M = 14.6g
A = 15.0g
(14.6g -
15.0g
15.0g) X 100
2.67% error
ACCURACCURACYACY
PRECISIPRECISIONONvv
s.s. Average is Average is close to the close to the
actual actual number/valunumber/valu
ee
Grouped Grouped close close
togethertogether(small range)(small range)
Accurate, Precise or Neither
5.1
5.2
5.0
417
638
962
13.24 12.99 13.15
AcceptAccepted ed
Value: Value: 5.145.14
Accepted Accepted Value: Value: 10.2510.25
AcceptAccepted ed
Value: Value: 947947
Trial 1 Trial 2 Trial 3
20.1 15.9 26.8
20.3 13.4 27.4
19.9 23.0 27.2
Accepted Accepted Value: 27.3Value: 27.3AA
PP
NNPP AA PPNN
PP
MASSMASS
Turn this Turn this knob to knob to make make sure sure
balance balance is zeroedis zeroed
Tenths Tenths placeplace
Ones Ones placeplace
Tens Tens placeplace
Hundreds Hundreds placeplace
100 200 300 400 500
10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 7 8 9 10
100 200 300 400 500
10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 7 8 9 10
100 200 300 400 500
10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 78 9 10
100 200 300 400 500
10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 7 8 9 10
140.5 g
74.8 g
500 g
30
40
VOLUMEVOLUMEGRADUATED CYLINDER GRADUATED CYLINDER
VS. BURETVS. BURETMEASURES MEASURES THE VOLUME THE VOLUME OF A LIQUID OF A LIQUID
What is What is this this
called?called?The The menimeniscusscus
!!
33.5 mL
MEASURES THE MEASURES THE VOLUME OF A VOLUME OF A
LIQUID RELEASED LIQUID RELEASED (USED IN (USED IN
TITRATIONS) TITRATIONS)
50
40
4.00 mL