Rolled throughput yield - RTY
Rolled throughput yield (RTY) is a similar measure to the first time through ratio or FTT, but it is interpreted as the probability that a unit of production or service will be produced/delivered correctly or of acceptable quality without it being scraped or rejected. So for example if a product is quoted as having a rolled throughput yield of 93%, it can be said that 93% of the time the product will be manufactured or service delivered without it being faulty or defective.
Its calculation is slightly different than FTT. It needs two measures to be calculated before the final measure can be computed. These two measures are the defects per unit (DPU) and the defects per inspection (DPI).
The defects per unit (DPU) can be calculated as:
(Defect per unit) / (total number of units)
The defects per inspection (DPI) can be calculated as:
(DPU) / (Number of inspections made)
Rolled throughput yield is then calculated as:
RTY= [ (1-DPI)^(z) ] ^(n)
Where z = number of inspections made
n = number of steps in production process or service delivery process.
Note: When we refer to number of inspections made, we are referring to the number of times within the production or service delivery process where anything important to the product or its quality is checked, measured, or tested.
This metric is usually used in six sigma, or by six sigma practitioners.