Are the LEP and SLD heavy flavour electroweak data combined correctly?

This talk forms part of a mini-workshop on Rb and Rc, motivated by the current discrepancy between the measurements and the Standard Model expectation. The question of whether the data are combined correctly is addressed here. The complete averaging procedure used to combine all the heavy flavour electroweak data from LEP and SLD is described with a view to convincing the reader that it is indeed correct. The sensitivity of the averages to the dominant sources of systematic error is also discussed.