You have just assembled your 4 new IKEA chairs and one is wobbling. What is the root cause? Is one part not manufactured accurately? Is one screw not doing its job or did you make a mistake in the assembly? BOB WOW is the technique to find out more about this by systematically exchanging parts. 


BOB & WOW (Best of Best and Worst of Worst) helps us identify and verify the cause of quality variation of products including assembly. This method - also known as “Component Search” compares and contrasts a best unit to a worst unit, so that the root causes for variation in quality become clearer.  



  • The product quality you are interested in must be measurable.
  • The product contains multiple parts (i.e. sub-assemblies) that can be exchanged.


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Please find instructions on each step below.

  1. Select two units as far apart in the characteristic of interest that you can readily find and measure them. These are your best of best and worst of worst.



How to run a BOB WOW Analysis. First step is to select 2 units far apart in the characteristic.

  1. Disassemble and Reassemble the units several times making sure all components of interest are included.
    Do you observe NO significant variation from one reassembly to another?
    If so (situation 1), continue with the next step, otherwise (situation 2), you´ve detected that the cause of variation is the assembly process.

How to run a BOB WOW Analysis. Step 2 of the Analysis

How to run a BOB WOW Analysis. Step 2 of the Analysis

  1. Swap one (or more) parts of the WOW unit to the BOB unit and plot their performance.
    Did the BOB unit with a part of the WOW unit significantly underperform? If so (2nd test with part C being from WOW and the rest from BOB), you´ve detected that the troubling part is that specific one. In this case, part C.

How to run a BOB WOW Analysis. Step 3 of the Analysis



In its most basic form, BOB WOW uses structured one-at-a-time experimentation until a significant variation is observed. This variation can arise from the assembly process of the unit or from one (or more) of its parts. Going deeper you could also find interaction effects and build DOEs (see Design of Experiments) on your component search.





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