Thursday, June 20, 2019

How to calculate percent error ?


Definition of Percent Error:

The percentage error, also known as percent error, is a measure of how innaccurate a measurement is, standardized to how large the measurement is. It is the relative error expressed in terms of per 100. The relative error is calculated as the absolute error divided by the magnitude of the exact value. The absolute error is the magnitude of the difference between the actual value and the estimated value.

Percentage error calculator
Percentage Error Calculator


What is the percent error?


Sometimes, we try to estimate the value of a particular quantity by making repeated measurements. For example, we can try to find out what is the gravitational acceleration by measuring the time of free fall from a specific height.The measured acceleration will probably deviate a bit from the actual acceleration of 9.80665 m/s². To check what is the relative - or percent - error, you need to know two values: the real value and observed (measured) one. 

Types of Error:


Percent error, margin of error, and standard error 


There are a lot of terms similar to percent error. To ensure you don't get confused and mix them up, we provide a short explanation of each of them here.
  • Percent error, or relative error: It is precisely what we described above - the relative difference between the observed and true value. You can apply the aforementioned percent error formula to calculate it. 
  •  Standard error is a value that can be calculated for a set of data. It is a statistical term that describes the accuracy with which a sample represents the whole population.
  • Margin of error, on the other hand, is closely related to the confidence interval. It can be calculated by multiplying the standard error with the z-score corresponding to a certain confidence level.


Steps to calculate percent error: 


  1. Subtract the accepted value from the experimental value.
  2. Take the absolute value of step 1
  3. Divide that answer by the accepted value.
  4. Multiply that answer by 100 and add the % symbol to express the answer as a percentage.
Note: occasionally, it is useful to know if the error is positive or negative. If you need to know the positive or negative error, this is done by dropping the absolute value brackets in the formula. In most cases, absolute error is fine. For example, in experiments involving yields in chemical reactions, it is unlikely you will obtain more product than theoretically possible.

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