# Percentage uncertainty and percentage difference

• koat
In summary, my teacher explained that percentage uncertainty is a measure of precision and percentage difference is a measure of accuracy. While you may have initially thought it was the other way round, your teacher is correct. In terms of precision and accuracy, uncertainty focuses on the measurement itself while difference compares it to a previously determined value. Without more context, it is difficult to determine what the values of 20% and 80% represent in terms of precision and accuracy.
koat
Hello
my teacher said that percentage uncertainty is a measure of precision and percentage difference a measure of accuracy.
i thought it's the other way round??
say if i have 20%
and 80%
what do these values tell me in terms of precision and accuracy?

koat said:
Hello
my teacher said that percentage uncertainty is a measure of precision and percentage difference a measure of accuracy.
i thought it's the other way round??
I think your teacher has it correct. For uncertainty and precision, you need not even know what the "correct" value is. For percent difference and also accuracy, you are comparing your measurement to the "correct" value that has already been determined by other means.
say if i have 20%
and 80%
what do these values tell me in terms of precision and accuracy?
I need more context to answer that question. What are you saying the 20% and the 80% numbers represent? 80% is not a very good value for either precision or accuracy.

## 1. What is percentage uncertainty?

Percentage uncertainty is a measure of the amount of error or variation in a measurement. It is calculated by dividing the absolute uncertainty (the smallest increment that can be measured by the instrument) by the measured value and multiplying by 100.

## 2. How is percentage uncertainty different from absolute uncertainty?

Absolute uncertainty is the smallest increment that can be measured by an instrument, while percentage uncertainty takes into account the magnitude of the measurement and expresses the error as a percentage of the measured value. In other words, absolute uncertainty is a fixed value while percentage uncertainty is relative to the measured value.

## 3. What is the significance of percentage uncertainty in scientific measurements?

Percentage uncertainty is important because it tells us how reliable a measurement is. The higher the percentage uncertainty, the less accurate the measurement is considered to be. It also helps us compare the accuracy of different measurements.

## 4. How is percentage difference calculated?

Percentage difference is calculated by taking the absolute value of the difference between two values, dividing it by the average of the two values, and multiplying by 100. This helps us compare the difference between two values of the same quantity.

## 5. Can percentage uncertainty and percentage difference be negative?

No, percentage uncertainty and percentage difference cannot be negative. The values of these calculations are always expressed as positive numbers, as they represent the magnitude of error or difference between two values. A negative value would indicate that the measured value is smaller than the calculated value, which is not possible.

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