accuracy and precision...PLEASE HELP!!!! URGENT! only those who can really answer!?

[timtim]

i am given 10 tubes. first 5 are filled with 1000 microlitre and the next 5 100 microlitre of solution. i had to weigh the empty tubes followed by with water. calculate the weight and find the volume n then find the % accuracy and precision.im supposed to comment on the results of my exp..how accurate and precise they are. after calculating, my % accuracy is -80% and %Coefficient variance(also the % precision) is 1.25% for the first 5 tubes. for the next 5, perentage accuracy is still -80% and % precision is 4.475%. does it mean it's more accurate or less? how do i explain the negative sign? and how do i compare and comment on the precisions? can there be any external factors affecting the results? we used micropipette for the measurements of the volumes.thanks

[motp]

accuracy means how close your result to the target. if 100%, that means you are very sharp. if +/-90%, that means your result is good, but there must be some reason behind it. And if your result is 0%, that means you are not accurate at all. So, the +/- doesn't really matter. It shows whether your are bit more or less.On the other hand, precision means the level of consistency between your result. You may get a +/-10% accuracy, but with 100% precision. If you get this kind of figure, it just simply means that there must be something wrong with your method.