Addition, multiplication, divison and subtraction of error

In summary, the conversation discusses the calculation of error in a mathematical expression involving two variables, p and q, with corresponding errors δx and δy. The formula R=p+q,p-q,p/q,pq is used to represent the sum, difference, quotient, and product of p and q. The speaker is seeking a method to determine the error in R. The suggested approach is to use standard error propagation, with examples provided for the four cases. There is some confusion and discussion about the notation used, as it may be considered mathematically incorrect.
  • #1
Apashanka
429
15
If given two variable of the form p=x±δx and q=y±δy where δx and δy are the error obtained while measuring p and q and x and y are it's absolute value obtained.
We define R=p+q,p-q,p/q,pq
In each of this case I want to know what will be the error in R.(e.g δR)
Thank you
 
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  • #3
Apashanka said:
We define R=p+q,p-q,p/q,pq
Mathematically, this doesn't make much sense. I get what you're trying to say, but R can't simultaneously be the sum, difference, product, and quotient of two values.
 
  • #4
Mark44: I believe the question is for .four cases.
 
  • #5
mathman said:
Mark44: I believe the question is for .four cases.
Yes, I understand that, but IMO R=p+q,p-q,p/q,pq is an abuse of notation where there is no explanation that this is shorthand.
 

1. How do you add or subtract errors?

When adding or subtracting errors, you simply add or subtract the values of the errors. For example, if you have an error of ±2 and you add it to another error of ±3, the resulting error would be ±5.

2. What is the rule for multiplying or dividing errors?

The rule for multiplying or dividing errors is to calculate the relative error for each individual measurement, and then add the relative errors together to get the overall relative error. For example, if you have a measurement with an error of ±5% and another measurement with an error of ±3%, the resulting error after multiplication would be ±8%.

3. Can you multiply or divide errors with different units?

No, you cannot multiply or divide errors with different units. Before performing any calculations, you must convert all errors to the same units. This ensures that the errors are consistent and can be accurately combined.

4. What is the difference between absolute and relative errors?

Absolute error is the difference between the measured value and the true value, while relative error is the absolute error divided by the true value. Relative error is often expressed as a percentage, while absolute error is expressed in the same units as the measured value.

5. How do you handle errors in a series of calculations?

When performing a series of calculations, it is important to carry the error through each step and combine them using the rules for addition, subtraction, multiplication, and division of errors. This ensures that the final result has an accurate error range that takes into account all previous calculations.

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