FTY & RTY

FTY- First Time Yield
RTY- Rolled Throughout Yield

Rolled Throughput Yield
We understand that a chain is only as strong as its weakest link; rolled throughput yield can never be greater than the lowest First Time Yield within the system we are measuring.
RTY = all steps in the process (in our example Steps or departments of A, B, C, D, E.)
RTY = 0.77 x 0.97 x 0.84 x 0.95 x 0.93
RTY = 0.554 x 100 = 55.4%
Chances of the product, service, or transaction going through this process the first time without rework, defect, or scrap is only 55.4% -- a lot of hidden factory to be found here! To immediately improve this performance, focus first on the process step with the lowest FTY. Needed is a very high individual FTY to be achieved for each process step in order to gain acceptable RTY.Traditional Yield is often a misleading perspective as it obscures the impact of inspection or rework. First Time Yield indicates the likelihood of an item passing through a process successfully the first time. This measurement includes considerations for inspection, rework and scrap.
RTY is the combined FTY of an entire process stream and indicates the likelihood of a product, service or transaction passing through all process steps successfully the first time. Considering that the complexity of modern processes usually far greater than five to ten process steps, it is easy to see that Six Sigma quality isn't optional; it's required if the organization is to remain viable.

Reference:
http://www.sixsigmadoctor.com/page9.html