Before you come to the laboratory, test yourself on your understanding of combining experimental errors by imagining that a quantity Q is computed from measured values of x and y according to
The values obtained experimentally are (to 90% confidence)
How much is Q uncertain due to the uncertainty of x?
How much is Q uncertain due to the uncertainty of y?
What is the value of Q, to 90% confidence? Be sure to show the uncertainties combine to obtain the net uncertainty in Q?