Measured Average

The following density measurements were made on a bar of iron: 7.58 g/mL, 8.02 g/mL, 7.83 g/mL, 7.80 g/mL, and 7.66 g/mL. The accepted value for iron's density is 7.85 g/ML. Find:

1) The average of this set of measurements 2) The average deviation of the set? 3) The relative average expressed as a percent?

For question 1 I got 7.778. For question 2 I got .126. I have no idea if these are right, and how to find the answer to number 3. Please explain your answers. Thank you!

Answers
The question does appear to be a little bit loose in its definitions. "Average" probably means "Mean" and your figure of 7.778 is correct. The average deviation of the set possibly means the mean deviation from the known value, which works out as 0.14 . The relative average possibly means the mean deviation from the mean of the set, which works out as 0.1264, or 12.64% . Research on the 'net was not entirely fruitful. Comments from an actual chemist (your teacher?) would be welcome.
ianmoth
18 January 2012
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