Error and percent error

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Example:

actual: 500.0 ft

trials

503.5 ft - 500 ft = 3.5 ft

502.8 ft - 500 ft = 2.8 ft

497.4 ft - 500 ft = -2.6 ft

erros = measured value - actual values

Percent error = |error|/ actual value x 100%

example:

3.5 ft / 500 ft x 100 % = .7 %

2.6 ft / 500 ft x 100% = .52 %

percent error = |measured value - actual value| / actual value x 100 %

Joshua uses his thermometer and finds the boiling point of ethyl alcohol to be 75°C. He looks in a reference book and finds that the actual boiling point of ethyl alcohol is 80°C. What is the percent error?

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percent error = |measured value - actual value| / actual value x 100 %

Joshua uses his thermometer and finds the boiling point of ethyl alcohol to be 75°C. He looks in a reference book and finds that the actual boiling point of ethyl alcohol is 80°C. What is the percent error?

75°C - 80°C = 5°C / 80°C = 0.0625 x 100 = 6.25 %

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percent error = |measured value - actual value| / actual value x 100 %

A student estimated a mass to be 250g, but upon carefully measuring it, found the actual mass to be 240g. What is the percent error?

measured value: 250g

actual value: 240g

250 - 240 = 10g / 240 = 0.042 x 100 = 4.2%

A student measured the temperature of boiling water and got an experimental

reading of 97.5°C. What is the percent error?

measured value: 97.5°C

actual value: 100°C

97.5 - 100 = 2.5 / 100 = 0.025 x 100 = 2.5%

An experimental measurement was taken of 10.4 mL and the actual

measurement was 9.7 mL. What is the percent error?

measured value: 10.4 mL

actual value: 9.7 mL

10.4 - 9.7 = 0.7 / 9.7 = 0.072 x 100 = 7.2%

Experimental = 62.5 g and accepted value = 65.2 g. Solve for percent error.

measured values : 62.5g

actual value: 62.2g

62.5 - 62.2 = 0.3 / 62.2 = 0.004 x 100 = 0.4%

Joe measured the volume of an object 5 times, and got results of: 34.5 mL,

34.9mL, 34.2 mL, 33.4 mL, and 35.9mL. What is his average experimental

result?

34.5 + 34-9 + 34.2 + 33.4 + 35.9 = 172.9 / 5 = 34.58

The actual volume of the object was 34.1 mL. What is the percent error of his

average result?

measured value: 34.58mL

actual value: 34.1mL

34.58 - 34.1 = 0.48 / 34.1 = 0.014 x 100 = 1.4%

A student estimated a mass to be 325g, but upon carefully measuring it, found

the actual mass to be 342g. What is the percent error?

measured value: 325g

actual value: 342g

325 - 342 = 17 / 342 = 0.049 x 100 = 4.9%

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percent error = |measured value - actual value| / actual value x 100 %

3. An object has a mass of 35.0 grams. On Anthony’s balance, it weighs 34.85 grams. What is the percent error of his balance?

34.85 - 35.0 = 0.15 / 35 = 0.004 x 100 = 0.4%

4. The concentration determined for an unknown sample of hydrochloric acid by a student is 0.1355 M. According to the instructor’s information, the true molarity (M) of this solution is 0.1364 M. What is the percent error in this experiment?

0.1355 - 0.1364 = 0.0009 / 0.1364 = 0.006598 x 100 = 0.6598%

5. The melting point of potassium thiocyanate determined by a student in the laboratory turned out to be 174.5 oC. The accepted value of this melting point is 173.2 oC. What is the percent error in this reading?

174.5°C - 173.2°C = 1.3 / 173.2 = 0.0075 x 100 = 0.75%

6. An object with an actual mass of exactly 0.54 g is given to 2 students. One student obtains a mass of 0.59 g for the object, while another says the mass is 0.49 g. Which of the students, if either has the greater percent error?

0.59 - 0.54 = 0.05 / 0.54 = 0.09259 x 100 = 9.259%

0.49 - 0.54 = 0.05 / 0.54 = 0.09259 x 100 = 9.259%

Both had the same percent error