1. Percent Error How to Calculate it. ERROR!

2. Error = Measured Value – Accepted Value Science references list the density of aluminum as being 2.7g/cm 3. Suppose you perform an experiment and your results show aluminum having a density of 2.8g/cm 3 Aluminum 2.7g/cm 3 Aluminum 2.8g/cm 3 Accepted Measured Error = 2.8g/cm 3 – 2.7g/cm 3 = 0.1g/cm 3 Error can be positive or negative but sometimes it isn’t very useful!

3. If you have a 10ft long table (accepted value) and your results state it is 5ft long (measured value) your error is 5ft. Goal line to Goal line, a football field is 300 feet (known value). If you measure its length and come up with 290ft your error is 10ft. Even though the first measurement was off by only 5ft, the second measurement which is off by 10ft is much better. In terms of percentages, the first measurement was off by 50% of the value whereas the second was only off by 3.3%. Error is 5ft out of 10  Error is 10ft but out of 300ft You can have an error of a million miles if you were measuring the distance to the sun but it would only be a 1-2% error because the sun is 93 million miles away!

4. Aluminum has an accepted value of 2.7g/cm 3.Suppose you perform an experiment and your results show aluminum as having a density of 2.8g/cm 3. What is your percent error? Get a difference. Compare to Accepted value. Multiply by 100.

5. A student measured the temperature of boiling water and got an experimental reading of 97.5°C. Calculate the % error. Get a difference. Compare to Accepted value. Multiply by 100.