accuracy and precision measurements are qualitative or quantitative. –qualitative measurements...

Accuracy and Precision

• Measurements are qualitative or quantitative.– Qualitative measurements give results that

are descriptive and non-numerical.• Example:

– Quantitative measurements give results that are definite, usually as numbers and units.

• Example:

Three targets Three targets with three with three arrows each arrows each to shoot.to shoot.

Can you hit the bull's-eye?Can you hit the bull's-eye?

Both accurate and precise

Precise but not accurate

Neither accurate nor precise

How do How do they they compare?compare?

Can you define accuracy and precision?Can you define accuracy and precision?

a)78.1 mL, 43.9 mL, 2 mL accurate precise should be 100mL both neither

NEITHERb) 68.1 mL, 68.2 mL, 68.0 mL accurate precise should be 68.1mL both neither

c) 98.0 mL, 98.2 mL, 97.9 mL accurate precise should be 100mL both neither

d) 72.0 mL, 60.3 mL, 68.1 mL accurate precise should be 100mL both neither

BOTH

BOTH

NEITHER

Accuracy and Precision

• Measurements work best when they are accurate and precise– Accuracy is a measure of how close a

measurement comes to the actual or true value of whatever is measured.

• To evaluate the accuracy of a measurement, it must be compared to the correct value.

– Precision is a measure of how close a series of measurements are to one another.

• The precision of a measurement depends on more than one measurement. Repeatability.

Accuracy and Precision

Accuracy and PrecisionDRAW THESE 4 in yourNotebook. Label what each Indicates.

Accuracy and Precision

• In this picture, all of the darts land on the bulls-eye which illustrates good precision and accuracy.

• In this picture, all of the darts land near each other, but away from the bulls-eye which illustrates good precision, but poor accuracy.

Accuracy and Precision

• Here the darts are not close to each other, but are close to the bulls-eye indicating poor precision, but good accuracy.

• Finally, the darts are not close to each other or near the bulls-eye indicating both poor accuracy and poor precision.

Accuracy and Precision

• What is the following an example of:• You did an experiment to see at what

degree water boiled in Celsius.You got the following results.T1- 65T2- 67T3 – 66 Accuracy or Precision????

PRECISION

Accuracy and Precision

A basketball player throws 100 free-throws; 95 of these balls go through the goal; 5 miss the goal entirely.

Describe the precision and accuracy of the free-throws.

95% accurate and 95% precise

The same player is having an off day; 5 balls go through the goal; the other 95 balls bounce off of the rim. Describe the precision and accuracy of the throws

5% accurate95% precise

.

Each of five students used the same ruler to measure the length of the same pencil. These data resulted: 15.33 cm, 15.34 cm, 15.33 cm, 15.33 cm, 15.34 cm. The actual length of the pencil was 15.85 cm. Describe the accuracy and precision for these measurements.

Precise but not accurate

Draw a target diagram that shows precision but not accuracy .

Draw a target diagram that shows accuracy but not precision

Draw a target diagram that shows both accuracy and precision

TOOLS WE NEEDTO READ TO BEACCURATE ANDPRECISE

Temperature ScalesTemperature Scales

Notice that 1 kelvin = 1 degree Celsius1 kelvin = 1 degree CelsiusKELVIN scale-absolute zero –temperatures doKELVIN scale-absolute zero –temperatures do not exist. ABSOLUTE 0=0not exist. ABSOLUTE 0=000 K K

Boiling point of Boiling point of waterwater

Freezing point Freezing point of waterof water

CelsiusCelsius

100 ˚C100 ˚C

0 ˚C0 ˚C

100˚C100˚C

KelvinKelvin

373 K373 K

273 K273 K

100 K100 K

FahrenheitFahrenheit

32 ˚F32 ˚F

212 ˚F212 ˚F

180˚F180˚F

Absolure Zero 00 K-273

Reading a MeterstickReading a Meterstick

. l. l22. . . . I . . . . I. . . . I . . . . I33 . . . .I . . . . I . . . .I . . . . I44. . cm. . cm

First digit (known)First digit (known) = 2 = 2 2.?? cm2.?? cm

Second digit (known)Second digit (known) = 0.7 = 0.7 2.7? cm2.7? cm

Third digit (estimated) between 0.05- 0.07Third digit (estimated) between 0.05- 0.07

Length reportedLength reported == 2.75 cm 2.75 cm

oror 2.74 cm 2.74 cm

oror 2.76 cm2.76 cm

Learning CheckLearning Check

. l8. . . . I . . . . I9. . . .I . . . . I10. . cm

What is the length of the line?What is the length of the line?

1) 9.6 cm 1) 9.6 cm

2) 9.62 cm 2) 9.62 cm

3) 9.63 cm3) 9.63 cm

How does your answer compare with your How does your answer compare with your

neighbor’s answer? Why or why not?neighbor’s answer? Why or why not?

ARE YOU ACCURATE OR PRECISE?ARE YOU ACCURATE OR PRECISE?

Zero as a Measured NumberZero as a Measured Number

. l3. . . . I . . . . I4 . . . . I . . . . I5. . cm

What is the length of the line?What is the length of the line?

First digitFirst digit 5.?? cm5.?? cm

Second digitSecond digit 55.0? cm.0? cm

Last (estimated) digit isLast (estimated) digit is 5.05.00 cm0 cm

Volume DisplacementVolume Displacement

A solid displaces a matching volume of water A solid displaces a matching volume of water when the solid is placed in water.when the solid is placed in water.

33 mL33 mL

25 mL 25 mL

190.2 g

37.4 g

105.6 g

Record to nearest tenth.

52.7 mL 6.62mL

Read frombottom

HOW MUCH? 350 mL