For the measured characteristic
- Precision is described by the range of values.
- Accuracy is described by the difference between the average value and the specified value.
Chocolate cookie widths
- Average = 5.10 "
- Range = 0.25"
- Average = 5.01"
- Range = 0.50"
Does that seem counterintuitive?
For a measurement or a measuring tool
- Precision is described by how many significant figures the tool gives you.
- Accuracy is described by how closely the measurement matches the value of a standard device and also by how accurate the standard is.
- One came from a store that sells drafting supplies. It is graduated in 16ths of an inch.
- The other, I made for myself after I loaned the store-bought ruler to a neighbor kid. I based it on one cubit (18"), the length from my elbow to my finger tips. When I graduated the cubit ruler in 50ths of an inch, I eyeballed the measurements and marked it by hand.