Effort Variance, Schedule Variance, Schedule Slippage

Effort Variance:
Effort Variance can be calculated as {(Actual Efforts-Estimated Efforts) / Estimated Efforts} *100.

Schedule Variance:
Just like above formula it is similarly calculated as.
{(Actual Duration - Estimated Duration)/Estimated Duration} *100

Schedule Slippage:
When a task has been delayed from its original baseline schedule then the amount of time that it has taken is defined as schedule slippage. Its calculation is as simple as.
(Actual End date - Estimated End date) / (Planned End Date – Planned Start Date) * 100

The GOAL should be to have all of them as ZERO.