Thursday, September 9, 2010

Accuracy and Sensitivity of Measuring Devices

Accuracy and Sensitivity


1. Accuracy 

  • refers to the agreement between experimental data and a known value.
  • how close to the actual or true accepted value are the measurement
    • you can think of it in terms of a bulls-eye in which the target is hit close to the center, yet the marks in the target aren't necessarily close to each other.




2. Precision
  • refers to how well experimental values agree with each other
  • how close are the individual measurements to one another
    • if you hit a bulls-eye precisely, then you are able to hit the same spot on the target each time, even though that spot may be distant from the center

    3. True Value
    • a given measurement that is set by the experts (i.e. scientists, professors, etc.)
    4. Experimental Value
    • the value gathered by the performer
    How to Compute For The Percent Error

    % Error=(True Value-Experimental Value)
                                     TV                       X100


    Exercises
    1. While doing an experiment, you were asked to measure a square block that was given to you. Each side was 15.72 cm. In your 3 trials you got: 15.23 cm , 14.92 cm  & 15.57 cm, an average of 15.24 cm. Find the percent error.


    =(15.72-15.24)/15.72 X 100
    =o.48/15.72X100
    =o.0305X100


    % error=3.05%


    2. In an experiment, you were asked to find out the measurement of a liquid inside the glass beaker. You had 3 trials in which you got: 25.32 ml, 27.45 ml & 26.24, having an average of 26.34 ml. The true value was 27.50 ml. Find the percent error.


    =(27.50-26.34)/27.50 X 100
    =1.16/27.50 X 100
    =o.0422X100


    % error= 4. 22%


    3.  You were inside a pet store when you saw puppies. You had estimated that there were 14 of them, though they were 15. Find the percent error.


    =(15-14)/15 X 100
    =1/15 X 100
    = o. 0667X 100


    % error= 6.67%


    4. While walking outside your house, you saw pink petals scattered everywhere. You estimated that there were 50 of them, when there was 52 petals. Find the percent error.




    =(52-50)/52 X 100
    =2/52 X 100
    =0.0385 X 100


    % error= 3.85 %


    5. While conducting an experiment, you were to measure a piece of block given to you. You had 4 trials to measure the block. You had arrived with these results: 14.25 cm, 14.26 cm, 14. 22 cm & 14. 23 cm. The true value was 14. 26 cm. What is your percent error?


    =(14.26-14.24)/14.26 X 100
    =o.o2/14.26 X 100
    =0.0014 X 100


    % error= 0.14 %


    Members:
    Cruz
    Gonzales, I.
    Mariano
    Pineda
    Sarmiento





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