To Physics 321'rs.

I've indicated that you should have begun reading the Taylor book.  Chapters 1 and 2 provide an introduction to uncertainty, and how uncertainty can be combined in the case of sum or product of uncertain quantities.  Chapter 2 provides the very important background on how to report uncertainties.   Chapter 3 discusses how uncertainties are propagated through more complicated combinations.  For example, in the first experiment, you measure angle in order to determine wavelength.  The calculation of wavelength involves the sine of the angle, so you would use the results of Ch 3 to figure out how to get the error in the sine, given an estimate in the error of the angle.  However, you don't need Ch 3 to make this estimate.  A very powerful, simple way to find out how errors propagate, particularly given the use of the computer and spreadsheet, is to repeat the calculation for lambda, varying theta by the amount you estimate to be your uncertainty of measurement. The results will display the "propagated uncertainty".

This technique is a the basis of "sensitivity analysis" wherein one determines how a calculated result depends upon variation of the inputs, and in particular, what are the really sensitive inputs.

One further point: when you quote uncertainty, you should ALWAYS distinguish between random and instrumental uncertainty.  This means you always have to repeat measurements in order to determine how random they are.