MEASURMENT, MEASURMENT, PERCENT PERCENT

ERROR, AND ERROR, AND ACCURACY VS. ACCURACY VS.

PRECISIONPRECISION

DETERMINING:DETERMINING: MASSMASS

& & VOLUMEVOLUME

MASSMASS

Turn this knob to make sure balance is zeroed

Tenths Tenths placeplace

Ones Ones placeplace

Tens Tens placeplace

Hundreds Hundreds placeplace

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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)

ACCURACYACCURACY PRECISIONPRECISIONvsvs..

ACCURACYACCURACY PRECISIONPRECISIONvsvs..

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

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100

A

B

C

D

E

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