measurment, percent error, and accuracy vs. precision
TRANSCRIPT
MEASURMENT, MEASURMENT, PERCENT PERCENT
ERROR, AND ERROR, AND ACCURACY VS. ACCURACY VS.
PRECISIONPRECISION
MASSMASS
Turn this knob to make sure balance is 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 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
140.5 g
74.8 g
500 g
30
40
VOLUMEVOLUMEGRADUATED CYLINDER VS. GRADUATED CYLINDER VS.
BURETBURETMEASURES THE
VOLUME OF A LIQUID
What is this
called?The
meniscus!
33.5 mL
MEASURES THE VOLUME OF A LIQUID RELEASED
(USED IN TITRATIONS)
50
40
4.00 mL
PERCENT ERRORPERCENT ERROR
Your Measured Value – Actual ValueYour Measured Value – Actual Value
Actual ValueActual Value XX 100100
Absolute Value sign: the Absolute Value sign: the difference cannot be negativedifference cannot be negative
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.
- 0.4g
15.0g
CALCULATIONCALCULATION
14.6g - 15.0g
15.0g 0.0260.0267 7
x 100x 100= =
2.67% error
Measured Value – Actual Value
Actual ValueX 100
ACCURACYACCURACY PRECISIONPRECISIONvsvs..
Average is close Average is close to the actual to the actual number/valuenumber/value
Grouped close Grouped 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
Accepted Accepted Value: 5.14Value: 5.14 Accepted Value: Accepted Value:
10.2510.25
Accepted Accepted Value: 947Value: 947
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 Value: Accepted Value: 27.327.3
AA
PP
NNPP AA PPNN
PP