- - several measurement results or other samples;
- - Calculator.
Measure at least 3-5 times to be able to calculate the actual value of the parameter.Add up the results and divide them by the number of measurements, you get the actual value, which is used instead of the true problems (it can not be determined).For example, if the result of the measurements gave 8, 9, 8, 7, 10, the actual value will be (8 + 9 + 8 + 7 + 10) / 5 = 8.4.
find the absolute error each measurement.For this measurement is subtracted from the result of the actual value, marks neglect.You will receive 5 absolute errors, one for each dimension.In the example they are equal range of 8-8.4 = 0.4, 9-8,4 = 0.6, range of 8-8.4 = 0.4, 7-8,4 = 1.4, 10-8,4= 1.6 (taken modules results).
To find the relative error each measurement, divide the absolute error to the actual (true) value.Then, multiply the result by 100%, is usually measured as a percentage of this value.Example get the relative error thus : δ1 = 0.4 / 0.048 = 8,4 (or 4,8%), δ2 = 0,6 / 8,4 = 0,071 (or 7,1%), δ3 =0.4 / 8.4 = 0.048 (or 4,8%), δ4 = 1,4 / 8,4 = 0,167 (or 16,7%), δ5 = 1,6 / 8,4 = 0,19 (or 19%).
In practice, for the most accurate representation of the error using the standard deviation.To find it, all squared absolute error of measurement and fold together.Then divide that number by the (N-1), where N - number of measurements.By calculating the square root of the result, you get a standard deviation characterizing measurement error.
To find the limiting absolute error , find the minimum number of knowingly exceeding the absolute error or equal to him.In this example, simply select the greatest value - 1.6.Also, sometimes it is necessary to find the limiting relative error , then get a number greater than or equal to the relative error, in the example it is 19%.
- find a measurement error