# Significant Figures/Accuracy and Precision - PowerPoint PPT Presentation

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Significant Figures/Accuracy and Precision. Accuracy vs Precision. Accuracy = Precision =. How close you are to the correct answer. How close your answers are to each other. Percent Error. You can quantify how accurate you are by calculating the percent error of your measurement

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Significant Figures/Accuracy and Precision

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## Significant Figures/Accuracy and Precision

### Accuracy vs Precision

Accuracy=

Precision =

How close you are to the correct answer

How close your answers are to each other

### Percent Error

You can quantify how accurate you are by calculating the percent error of your measurement

Percent Error = Experimental Value – Accepted Value x 100

Accepted Value

Absolute Value Sign – Make this value positive

### Example

In the lab, you measure the mass of an object to be 3.56 g. The actual mass of the object is 4.23 g. What is the percent error?

Percent Error = Experimental Value – Accepted Value x 100

Accepted Value

Percent Error = 3.56g – 4.23g x 100 = 15.8%

4.23

### Measurement

When you record a measurement, always record all certain digits PLUS one uncertain digit.

These are called the

significant figures (digits)

of the measurement

### Measurement

If the measurement lands on a line, the uncertain number is 0!

0.90 cm

### Sig Fig Rules

Rules for Identifying Significant Figures (Sig Figs)

(Found on your STAAR Reference Sheet)

• Non-zero digits and zeros between non-zero digits are always significant. 145 (3 s.f.) , 2001 (4 s.f.)

2. Leading zeros are not significant. 0.00032 (2 s.f.)

3. Zeros to the right of all non-zero digits are only significant if a decimal point is shown.

3.400 (4 s.f.), 200 (1 s.f.)

### Practice!

Determine the number of sig. figs. in the following numbers.

0.0032

2sf

2sf

3200

4sf

4sf

32.00

3002

32

2sf

### Mult./Div. Rules

Rounding multiplication/division calculations

to the proper number of sig figs

Round the answer to the lowest number of sig figs in the calculation

23.0 x 2.003 x 0.245 = 11.286905 =

3sf 4sf 3sf

11.3

3 sf

### Practice!

Perform the following calculations and round the answer to the proper number of sig figs.

450 = 3.947368421 =

114

84 x 31.221 = 2622.564 =

2 sf

2 sf

3.9

3 sf

2 sf

5 sf

2 sf

2600

### Add./Sub. Rules

Rounding addition/subtraction calculations

to the proper number of decimals

Round the answer to the lowest number of decimals (dp) in the calculation

23.0 + 2.003 + 0.24 = 25.243 =

25.2

1 dp

2 dp

1 dp

3 dp

### Practice!

Perform the following calculations and round the answer to the proper number of decimal places.

39.64 + 1.3 = 40.94 =

195.4 - 193 = 2.4 =

1 dp

2 dp

1 dp

40.9

0 dp

0 dp

1 dp

2