Rolled Throughput Yield (RTY) Calculations for a Sequential Process

[HDR]

If we have a a sequential process A -> B - > C, and for each process we collect the First pass yield weekly. What is the best way to calculate RTY for the month. Do we just do the following

(sum of # Rejected for month from process A / sum of # Tested for month in Process A) * (sum of # Rejected for month from process B / sum of # Tested for month in Process B) * (sum of # Rejected for month from process C / sum of # Tested for month in Process C)

Or do we have to calculate the RTY numbers for each week and somehow roll up a number for the month .. basically .. what is the best way to calculate a monthly RTY for a prcess that we collect data for on a weekly basis????

 

[wmarhel]

Re: RTY Calcualation ???

What is the significance of a monthly number? The shorter the interval for the calculation (daily vs. weekly vs. monthly) makes more sense. Otherwise, your just accepting the results and tracking them. Four weeks of data just to spit a number out at the end seems a little pointless. Calculating RTY (your example calculation is correct) has a couple of purposes:

1) Determine the overall effectiveness/reliability of the process

2) Identify which step is most detrimental to the process and apply corrective measures

3) Determine if any particular step in processes exceeds the "typical" level of defects

You answered your own question in the last paragraph:

Or do we have to calculate the RTY numbers for each week and somehow roll up a number for the month .. basically .. what is the best way to calculate a monthly RTY for a prcess that we collect data for on a weekly basis????

If you collect the data weekly.....report it weekly.

Wayne

 

[Marc]

Re: RTY Calculations for a Sequential Process

Also see: How to define and Calculate the DPU, DPMO, Yield, Rolled Throughput Yield (RTY)