control Schedule - variance analysis - few questions

Hi,

1. Schedule variance anlysis refers to a term called "Total Float Variance". I could not follow it well. do we keep track of total float deviation from the baseline schedule, and probably draw a run chart of float deviation ? ( float variance = baseline float - current float)

2. After thought, it makes sense to use Schedule deviation rather than schedule variance for EV - PV, since variance has a different statistical meaning. any comments ?

3. Fundamentally, I could not understand how the difference between two costs (Planned value and Earned vlue) gives the notion of time (schedule) performance. any thoughts?

Thanks in advance, Chary