Comparison of Two Values

Often one wants to compare two values such as comparing a result with an expected value, or comparing two different results. This is usually done in one of two ways.

a) Absolute Difference

Comparisons can be made by taking the absolute difference (eg. my value is 10 joules less than the expected). In this case, one of the values (either your value or the value compared) needs to be stated for the difference to be put into context (An expected value of 100,000 joules would mean the my value was quite good. Similarly an expected value of 20 joules would say the opposite)

b) Percentage Difference

The percentage difference expresses the difference between two values as a percentage (eg. the difference was 10%). For this to be an accurate value one must also state from which value the percent was taken.

For example, writing that my resistance value is 10% less than shown by the color code implies it was calculated as;

or saying that the color code resistance is 9.6% higher than my value implies;

Note, one can divide by either number ("accepted value" or your value) but must state the percent difference in its appropriate context. To easily remember how to correctly write a sentence with percent difference, notice that the value that one divides by is at the end of the sentence (the target value).

Also note, Percent difference is calculated without uncertainties.