Accuracy, Precision, and Percent Error

Key Questions

• How can precision be measured?

  Answer:

  Maybe by `sigma_d`, `"the standard deviation..."`

  Explanation:

  As you should know, `"accuracy"` refers to the closeness of a measurement to the TRUE value; whereas `"precision"` refers to the repeatability of a measurement. Precise measurements may be inaccurate due to some systematic error, and accurate measurements may be imprecise given the scatter, i.e. the range of a series of measurements.

  You will introduced to a range of ways of dealing with error in your analytical chemistry text. This will also include formal definitions of `sigma_d`...

  anor277 · 1 · Jul 14 2018

• How can accuracy of a measurement be improved?
• How can percent error be reduced?
• How can precision be improved?
• How can precision be measured?
• What is precision in chemistry?
• What percent error is too high?
• Question #8fc5c
• How is mass measured?
• Question #45bf3
• What do call the curved surface of water in a measuring cylinder?
• Question #34135
• Question #6dc15
• Question #0710f
• Question #1f0de
• Question #81194
• A student obtains a percent error of 20% after finding that the true value for the mass of an object is 50 grams. What is the student's value?
• Question #f564c
• What is percent error/percent deviation?
• A student measures the mass of a sample as 9.67 g. What is the percent error, given that the correct mass is 9.82 g?
• What is parallax error in chemistry?
• 5,7% of error in a Hydrated Crystal lab, is it too high?
• What is a meniscus? Why is it necessary to know about it when measuring liquids?
• What is the percent error if the accepted value is 80g and the measured is 82g?
• Question #15837
• Question #8063f
• The melting point of a white solid substance was determined in four repeated trials to be 56.0°C, 55.0°C, 57.5°C, 55.5°C. What temperature should be reported as the melting point as a result of these trials?
• A student measured the mass of a small object and found it to be 56.0 grams. The object's mass is known to be 55.0 grams. What is the percent of error in the student's measurement?
• Why is using a graduated cylinder more accurate than using a beaker?
• A chemist measures 340 grams of sodium acetate. What is this in kilograms?
• How would you find the greatest possible error for the measurement 0.991 g?
• You measure a piece of rope and find its length to be 12 m. How do you find the percent error of this measurement?
• How do you find the percent error of the measurement 11.56 cm?
• What is the difference between accuracy and precision in scientific experiments?
• Is it possible to be precise but not accurate?
• What is accuracy?
• What is precision?
• Does accuracy refers to the level of detail to which a measurement is taken?
• Is precision a measure of how close an answer is to the actual or expected value?
• Aset of data is highly precise, what does this indicate about the accuracy of the data?
• What is precision error in chemistry?
• What is the process of deliberately adding very small amount of impurities to a pure substance called?
• Which is the most accurate method for measuring volumes of liquids, a beaker or a graduated cylinder?
• Accuracy refers to the freedom from error or mistake of a measuring device. How accurate is a volumetric flask as a measuring instrument?
• Which cylinder would be more accurate for measuring 5 ml of solution: the 100 ml cylinder or the 10 ml cylinder?
• What is the difference between Accepted Value vs. Experimental Value?
• Given the following, what the actual volume of the pipet?
• The accepted length of a steel pipe is 5.5 m. How do you calculate the percent error for each of these measurements?
• What sort of meniscus does mercury form in a glass vessel?
• All measurements contain some error. Why is this a true statement?
• In the measurement 0.544 m, which digit is the estimated?
• How can I improve my accuracy and precision in lab measurements?
• What is percent error?
• What is the degree to which a measurement approaches a standard value?
• Question #34fbb
• Astudent measures the depth of a swimming pool to be 2.04 meters at its deepest end. The accepted value is 2.00 m. What is the student's percent error?
• What are two good scientific reason to account for any experimental error?
• Are there any circumstances under which an accurate measurement may not be precise?
• How do you find percent change?
• A test was 125 questions and you got 107 of them correct, what was your percent error?
• In a scientific experiment, the mass of an object was determined to be 20.450 g, 20.313 g, and 21.013 g. What is the mean mass of the object? And the average deviation from the mean?
• How many water has been dispensed if the initial buret reading was 0.73 mL and the final is 25.98 mL?
• What does it mean to repeat measurements often which are often dependent on the certainty with which an estimation can be made?
• What is the term describing how correct a measurement is?
• How should you always read a graduated cylinder?
• If three variables were changed at one time, what would happen to the accuracy of the conclusions made for an experiment?
• These data show repeated measurements of the same object which has a known mass of 5.38 grams. Which measurement is most accurate?
• An experiment produced 0.10 g `CO_2`, with a volume of 0.056 L at STP. If the accepted density of `CO_2` at STP is 1.96 g/L, what is the approximate percent error?
• An experiment produced 0.10 g `CO_2`, with a volume of 0.056 L at STP. If the accepted density of `CO_2` at STP is 1.96 g/L, what is the approximate percent error?
• What was the most probable cause of error in the following problem?
• How would you define accuracy and precision?
• Does any one know what the random errors are in enthalpy of combustion of alcohols experiment? like methanol, ethanol, etc.
• How would you create a sketch illustrating the difference between the terms accuracy and precision in scientific measurement?
• Suppose you calculated the speed of light in an unknown substance to be `4.00 xx10^8` m/s. How could you tell if you made an error in your calculations?
• An object was measured by a worker as 17.4 cm long; however, the manufacturer specifications list the length of the object at 17.9 cm. What is the percent error in the workers measurement?
• Question #a8292
• Question #2bf80
• Question #14f6c
• A vernier calipers has an error of `2%` in length, `1%` in breadth and `3%` in thickness, What is the maximum percentage error in measuring volume with it?
• Question #f903e
• Question #2c114
• A handbook gives the density of calcium as `"1.62 g/cm"^3`. What is the percent error of a density calculation of `"1.37 g/cm"^3` based on lab measurements?
• The experimental calculation of the specific heat of aluminum was found to be 156 cal/g °C, but the actual value was given as 185 cal/g°C. What is the percent error?
• 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?