Objectives

The student will be able to:

●Distinguish between accuracy and precision●Use significant figures in measurements and calculations

Accuracy and Precision

●Careful measurements are _________ in science

●No measurement is perfect

●Two terms that describe this imperfection:

oAccuracy: the extent to which a reported measurement approaches the ___________of the quantity measured

oPrecision: the degree of ___________ or refinement of a measurement

Accuracy vs Precision

Sources of Error

Problems with accuracy are due to error

●Human Error: Mistakes made in _________ an instrument or recording the results

● Method Error: When measurements are taken using different methodsoParallax: An overestimate or underestimate due to the improper

viewing of a measuring device

● ________ Error: Improperly displayed measurements due to poorly calibrated devices

Precision and Significant Figures

●Significant figures (Sig Figs) describe the ____________ of a measuring device

● Significant Figures: those digits in a measurement that are known with certainty ______ the first digit that is _________

Review of Sig Fig RulesNonzero Digits are __________ significant!• 46.3 has 3 sig figs.

Zero Rules:●Zeros between other ___________ digits are ___________

- 50.3 m has three sig figs●Zeros _____________of nonzero digits are ____ significant

- 0.553 m has three sig figs●Zeros that are _______ at the end of the number and to the

________ of the decimal point are significant. - 50.00 has four sig figs

●Zeros at the end of a number, but to the left of the decimal point may not be significant. If the place wasn’t estimated, it’s not significant. *Example: 100 has 1 significant figure*

LETS PLAY: THE SIG FIG IS RIGHT

Determine how many sig figs are in the following quantities:

1.5.03 2.3.0025 3.0.0892 4.0.00008 5.57.00 6.2.000000 7.2100 8.0.75

SIG FIG

Rules For Calculating Sig Figs

●Addition and Subtraction:oFinal answer should have the ________ number of sig figs to

the right of the decimal place as the number with the _________ number of digits to the right of the decimal

●Multiplication and Division:oThe final answer should have the ________ number of sig figs

as the measurement having the __________number of sig figs

Rounding Rule

●If the digit being rounded is less than five, round down

●If the digit being rounded is five or greater, round up

LETS PLAY: THE SIG FIG IS RIGHT... AGAIN!  

Determine what the final answer would look like after performing the indicated operation for the following questions:

-97.3 + 5.85 -123 x 5.35 -57 + 3.021  x 74.3

SIG FIG

AGAIN

Wrap Up

Answer the following questions:

● Why are significant figures important?

● What steps could an experimenter take to ensure that their experiment is as accurate as possible?